Articulating including antagonistic controls for articulation and calibration

ABSTRACT

A method of homing a drive input of a robotic surgical tool includes recording and storing a home position of the drive input in a memory included in the robotic surgical tool, establishing a slow zone for the drive input encompassing a known angular magnitude away from the home position, storing the slow zone in the memory, rotating the drive input toward the home position, and slowing a rotation speed of the drive input upon reaching the slow zone.

BACKGROUND

Minimally invasive surgical (MIS) instruments are often preferred overtraditional open surgical devices due to the reduced post-operativerecovery time and minimal scarring. The most common MIS procedure may beendoscopy, and the most common form of endoscopy is laparoscopy, inwhich one or more small incisions are formed in the abdomen of a patientand a trocar is inserted through the incision to form a pathway thatprovides access to the abdominal cavity. The trocar is used to introducevarious instruments and tools into the abdominal cavity, as well as toprovide insufflation to elevate the abdominal wall above the organs. Theinstruments can be used to engage and/or treat tissue in a number ofways to achieve a diagnostic or therapeutic effect.

Each surgical tool typically includes an end effector arranged at itsdistal end. Example end effectors include clamps, graspers, scissors,staplers, and needle holders, and are similar to those used inconventional (open) surgery except that the end effector of each tool isseparated from its handle by an approximately 12-inch long shaft. Acamera or image capture device, such as an endoscope, is also commonlyintroduced into the abdominal cavity to enable the surgeon to view thesurgical field and the operation of the end effectors during operation.The surgeon is able to view the procedure in real-time by means of avisual display in communication with the image capture device.

Surgical staplers are one type of end effector capable of cutting andsimultaneously stapling (fastening) transected tissue. Alternatelyreferred to as an “endocutter,” the surgical stapler includes opposingjaws capable of opening and closing to grasp and release tissue. Oncetissue is grasped or clamped between the opposing jaws, the end effectormay be “fired” to advance a cutting element or knife distally totransect grasped tissue. As the cutting element advances, staplescontained within the end effector are progressively deployed to sealopposing sides of the transected tissue.

Surgical tools include articulable wrists configured to permit anglingof the end effector into a desired orientation. An articulable wristhaving a joint that provides a high degree of freedom is needed. Alsoneeded is a system for powering the articulable wrist such that it maymove smoothly through tissue, which provides an external load on thewrist, and maintain a position into which it has been articulated whensubjected to such external load. Moreover, systems for homing the driveinputs of the surgical are needed that, upon installing the surgicaltool in the robotic manipulator, reposition the articulable wrist intoan unarticulated orientation such that it may be inserted through atrocar and into the abdominal cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent disclosure, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, withoutdeparting from the scope of this disclosure.

FIG. 1 is a block diagram of an example robotic surgical system that mayincorporate some or all of the principles of the present disclosure.

FIG. 2 is an example embodiment of one of the master control consoles ofFIG. 1 .

FIG. 3 depicts one example of the robotic manipulator of FIG. 1 ,according to one or more embodiments.

FIG. 4 is an isometric side view of an example surgical tool that mayincorporate some or all of the principles of the present disclosure.

FIG. 5 illustrates potential degrees of freedom in which the wrist ofFIG. 4 may be able to articulate (pivot).

FIG. 6 is a bottom view of the drive housing of FIG. 4 , according toone or more embodiments.

FIGS. 7A and 7B are exposed isometric views of the interior of the drivehousing of FIG. 4 , according to one or more embodiments.

FIGS. 8A and 8B are exposed isometric views depicting example geartrains within the surgical tool of FIGS. 7A-7B.

FIGS. 9A and 9B are exposed bottom views of the surgical tool of FIG. 4.

FIG. 10A illustrates an example articulable wrist that may be utilizedin the surgical tool of FIGS. 9A and 9B, according to one or moreembodiments of the disclosure.

FIG. 10B is an exploded view of the articulable wrist of FIG. 10A,according to one or more embodiments of the disclosure.

FIGS. 11A-11C illustrate various example algorithms programmable intothe computer system of FIG. 6 to control operation of the drivers ofFIG. 6 , according to various embodiments of the present disclosure.

FIG. 12 illustrates a set of graphs showing an example operation of anexample homing system, according to one or more embodiments of thedisclosure.

FIG. 13 illustrates to exposed view of an exemplary joint of the wristin FIGS. 10A-10B.

FIG. 14 is a schematic of an exemplary method for controllingarticulation of the joint of FIG. 13 , according to one or moreembodiments of the disclosure.

FIGS. 15A and 15B are top exposed views of the wrist of FIG. 13illustrating example operation of the method of FIG. 14 .

FIG. 16 is a schematic of another exemplary method for controllingarticulation of the joint of FIG. 13 , according to one or moreembodiments of the disclosure.

FIGS. 17A and 17B are plots illustrating an exemplary differentialcontrol for actuating the wrist, according to one or more embodiments ofthe disclosure.

FIG. 18 illustrates a force versus distance curve of an exemplaryclosure system, according to one or more embodiments of the disclosure.

DETAILED DESCRIPTION

The present disclosure is related to robotic surgery and, moreparticularly, to an articulable wrist or joint used to position an endeffector of a surgical tool, to systems for articulating the wrist intoa desired position when subject to an external load and maintaining thatposition when subject to the load, systems for homing the articulablewrist, and systems for ensuring accurate positioning of the wrist.

FIGS. 1-3 illustrate the structure and operation of an example roboticsurgical system and associated components thereof. While applicable torobotic surgical systems, it is noted that the principles of the presentdisclosure may equally or alternatively be applied to non-roboticsurgical systems, without departing from the scope of the disclosure.

FIG. 1 is a block diagram of an example robotic surgical system 100 thatmay incorporate some or all of the principles of the present disclosure.As illustrated, the system 100 can include at least one master controlconsole 102 a and at least one robotic manipulator 104. The roboticmanipulator 104 may be mechanically and/or electrically coupled to orotherwise include one or more robotic arms 106. In some embodiments, therobotic manipulator 104 may be mounted to a transport cart (alternatelyreferred to as an “arm cart”) that enables mobility of the roboticmanipulator 104 and the associated robotic arms 106. Each robotic arm106 may include and otherwise provide a tool driver where one or moresurgical instruments or tools 108 may be mounted for performing varioussurgical tasks on a patient 110. Operation of the robotic arms 106, thecorresponding tool drivers, and the associated tools 108 may be directedby a clinician 112 a (e.g., a surgeon) from the master control console102 a.

In some embodiments, a second master control console 102 b (shown indashed lines) operated by a second clinician 112 b may also help directoperation of the robotic arms 106 and the tools 108 in conjunction withthe first clinician 112 a. In such embodiments, for example, eachclinician 112 a,b may control different robotic arms 106 or, in somecases, complete control of the robotic arms 106 may be passed betweenthe clinicians 112 a,b. In some embodiments, additional roboticmanipulators having additional robotic arms may be utilized duringsurgery on a patient 110, and these additional robotic arms may becontrolled by one or more of the master control consoles 102 a,b.

The robotic manipulator 104 and the master control consoles 102 a,b maycommunicate with one another via a communications link 114, which may beany type of wired or wireless communications link configured to carrysuitable types of signals (e.g., electrical, optical, infrared, etc.)according to any communications protocol. The communications link 114may be an actual physical link or it may be a logical link that uses oneor more actual physical links. When the link is a logical link the typeof physical link may be a data link, uplink, downlink, fiber optic link,point-to-point link, for example, as is well known in the computernetworking art to refer to the communications facilities that connectnodes of a network. Accordingly, the clinicians 112 a,b may be able toremotely control the robotic arms 106 via the communications link 114,thus enabling the clinicians 112 a,b to operate on the patient 110remotely.

FIG. 2 is one example embodiment of the master control console 102 athat may be used to control operation of the robotic manipulator 104 ofFIG. 1 . As illustrated, the master control console 102 a can include asupport 202 on which the clinician 112 a,b (FIG. 1 ) can rest his/herforearms while gripping one or more user input devices 203, one in eachhand. The user input devices 203 may comprise, for example, physicalcontrollers such as, but not limited to, a joystick, exoskeletal gloves,a master manipulator, etc., and may be movable in multiple degrees offreedom to control the position, orientation, and operation of thesurgical tool(s) 108 (FIG. 1 ). In some embodiments, the master controlconsole 102 a may further include one or more foot pedals 204 engageableby the clinician 112 a,b to change the configuration of the surgicalsystem and/or generate additional control signals to control operationof the surgical tool(s) 108.

The user input devices 203 and/or the foot pedals 204 may be manipulatedwhile the clinician 112 a,b (FIG. 1 ) views the procedure via a visualdisplay 206. Images displayed on the visual display 206 may be obtainedfrom an endoscopic camera or “endoscope.” In some embodiments, thevisual display 206 may include or otherwise incorporate a force feedbackmeter or “force indicator” that provides the clinician 112 a,b with avisual indication of the magnitude of force being assumed by thesurgical tool (i.e., a cutting instrument or dynamic clamping member)and in which direction. As will be appreciated, other sensorarrangements may be employed to provide the master control console 102 awith an indication of other surgical tool metrics, such as whether astaple cartridge has been loaded into an end effector or whether ananvil has been moved to a closed position prior to firing, for example.

FIG. 3 depicts one example of the robotic manipulator 104 that may beused to operate a plurality of surgical tools 108, according to one ormore embodiments. As illustrated, the robotic manipulator 104 mayinclude a base 302 that supports a vertically extending column 304. Aplurality of robotic arms 106 (three shown) may be operatively coupledto the column 304 at a carriage 306 that can be selectively adjusted tovary the height of the robotic arms 106 relative to the base 302, asindicated by the arrow A.

The robotic arms 106 may comprise manually articulable linkages,alternately referred to as “set-up joints.” In the illustratedembodiment, a surgical tool 108 is mounted to corresponding tool drivers308 provided on each robotic arm 106. Each tool driver 308 may includeone or more drivers or motors (sometimes referred to as drivers 610 a-f)used to interact with a corresponding one or more drive inputs of thesurgical tools 108, and actuation of the drive inputs causes theassociated surgical tool 108 to operate.

One of the surgical tools 108 may comprise an image capture device 310,such as an endoscope, which may include, for example, a laparoscope, anarthroscope, a hysteroscope, or may alternatively include some otherimaging modality, such as ultrasound, infrared, fluoroscopy, magneticresonance imaging, or the like. The image capture device 310 has aviewing end located at the distal end of an elongate shaft, whichpermits the viewing end to be inserted through an entry port into aninternal surgical site of a patient's body. The image capture device 310may be communicably coupled to the visual display 206 (FIG. 2 ) andcapable of transmitting images in real-time to be displayed on thevisual display 206.

The remaining surgical tools may be communicably coupled to the userinput devices held by the clinician 112 a,b (FIG. 1 ) at the mastercontrol console 102 a (FIG. 2 ). Movement of the robotic arms 106 andassociated surgical tools 108 may be controlled by the clinician 112 a,bmanipulating the user input devices. As described in more detail below,the surgical tools 108 may include or otherwise incorporate an endeffector mounted on a corresponding articulable wrist pivotally mountedon a distal end of an associated elongate shaft. The elongate shaftpermits the end effector to be inserted through entry ports into theinternal surgical site of a patient's body, and the user input devicesalso control movement (actuation) of the end effector.

In use, the robotic manipulator 104 is positioned close to a patientrequiring surgery and is then normally caused to remain stationary untila surgical procedure to be performed has been completed. The roboticmanipulator 104 typically has wheels or castors to render it mobile. Thelateral and vertical positioning of the robotic arms 106 may be set bythe clinician 112 a,b (FIG. 1 ) to facilitate passing the elongateshafts of the surgical tools 108 and the image capture device 310through the entry ports to desired positions relative to the surgicalsite. When the surgical tools 108 and image capture device 310 are sopositioned, the robotic arms 106 and carriage 306 can be locked inposition.

FIG. 4 is an isometric side view of an example surgical tool 400 thatmay incorporate some or all of the principles of the present disclosure.The surgical tool 400 may be the same as or similar to the surgicaltool(s) 108 of FIGS. 1 and 3 and, therefore, may be used in conjunctionwith a robotic surgical system, such as the robotic surgical system 100of FIG. 1 . As illustrated, the surgical tool 400 includes an elongatedshaft 402, an end effector 404, an articulable wrist 406 (alternatelyreferred to as a “wrist joint”) that couples the end effector 404 to thedistal end of the shaft 402, and a drive housing 408 coupled to theproximal end of the shaft 402. In applications where the surgical tool400 is used in conjunction with a robotic surgical system, the drivehousing 408 can include coupling features that releasably couple thesurgical tool 400 to the robotic surgical system. The principles of thepresent disclosure, however, are equally applicable to surgical toolsthat are non-robotic and otherwise capable of manual manipulation.

The terms “proximal” and “distal” are defined herein relative to arobotic surgical system having an interface configured to mechanicallyand electrically couple the surgical tool 400 (e.g., the drive housing408) to a robotic manipulator. The term “proximal” refers to theposition of an element closer to the robotic manipulator and the term“distal” refers to the position of an element closer to the end effector404 and thus further away from the robotic manipulator. Moreover, theuse of directional terms such as above, below, upper, lower, upward,downward, left, right, and the like are used in relation to theillustrative embodiments as they are depicted in the figures, the upwardor upper direction being toward the top of the corresponding figure andthe downward or lower direction being toward the bottom of thecorresponding figure.

The surgical tool 400 can have any of a variety of configurationscapable of performing one or more surgical functions. In the illustratedembodiment, the end effector 404 comprises a surgical stapler,alternately referred to as an “endocutter,” configured to cut and staple(fasten) tissue. As illustrated, the end effector 404 includes opposingjaws 410, 412 configured to move (articulate) between open and closedpositions. The opposing jaws 410, 412, however, may alternately formpart of other types of end effectors with jaws such as, but not limitedto, a tissue grasper, surgical scissors, an advanced energy vesselsealer, a clip applier, a needle driver, a babcock including a pair ofopposed grasping jaws, bipolar jaws (e.g., bipolar Maryland grasper,forceps, a fenestrated grasper, etc.), etc. One or both of the jaws 410,412 may be configured to pivot to actuate the end effector 404 betweenthe open and closed positions.

In the illustrated embodiment, the first jaw 410 may be characterized orotherwise referred to as a “cartridge” jaw, and the second jaw 412 maybe characterized or otherwise referred to as an “anvil” jaw. Morespecifically, the first jaw 410 may include a frame that houses orsupports a staple cartridge, and the second jaw 412 is pivotallysupported relative to the first jaw 410 and defines a surface thatoperates as an anvil to form staples ejected from the staple cartridgeduring operation. In use, the second jaw 412 is rotatable between anopen, unclamped position and a closed, clamped position. In otherembodiments, however, the first jaw 410 may move (rotate) relative tothe second jaw 412, without departing from the scope of the disclosure.

The wrist 406 enables the end effector 404 to articulate (pivot)relative to the shaft 402 and thereby position the end effector 404 atdesired orientations and locations relative to a surgical site. FIG. 5illustrates the potential degrees of freedom in which the wrist 406 maybe able to articulate (pivot). The wrist 406 can have any of a varietyof configurations. In general, the wrist 406 comprises a jointconfigured to allow pivoting movement of the end effector 404 relativeto the shaft 402. The degrees of freedom of the wrist 406 arerepresented by three translational variables (i.e., surge, heave, andsway), and by three rotational variables (i.e., Euler angles or roll,pitch, and yaw). The translational and rotational variables describe theposition and orientation of a component of a surgical system (e.g., theend effector 404) with respect to a given reference Cartesian frame. Asdepicted in FIG. 5 , “surge” refers to forward and backwardtranslational movement, “heave” refers to translational movement up anddown, and “sway” refers to translational movement left and right. Withregard to the rotational terms, “roll” refers to tilting side to side,“pitch” refers to tilting forward and backward, and “yaw” refers toturning left and right.

The pivoting motion can include pitch movement about a first axis of thewrist 406 (e.g., X-axis), yaw movement about a second axis of the wrist406 (e.g., Y-axis), and combinations thereof to allow for 360°rotational movement of the end effector 404 about the wrist 406. Inother applications, the pivoting motion can be limited to movement in asingle plane, e.g., only pitch movement about the first axis of thewrist 406 or only yaw movement about the second axis of the wrist 406,such that the end effector 404 moves only in a single plane.

Referring again to FIG. 4 , the surgical tool 400 may include aplurality of drive members or the like (obscured in FIG. 4 ) that formpart of an actuation system configured to facilitate articulation of thewrist 406 and actuation (operation) of the end effector 404 (e.g.,clamping, firing, rotation, articulation, energy delivery, etc.). Somedrive members may extend to the wrist 406, and selective actuation ofthese drive members causes the end effector 404 to articulate (pivot)relative to the shaft 402 at the wrist 406. The end effector 404 isdepicted in FIG. 4 in the unarticulated position where a longitudinalaxis A₂ of the end effector 404 is substantially aligned with thelongitudinal axis A₁ of the shaft 402, such that the end effector 404 isat a substantially zero angle relative to the shaft 402. In thearticulated position, the longitudinal axes A₁, A₂ would be angularlyoffset from each other such that the end effector 404 is at a non-zeroangle relative to the shaft 402.

Other drive members may extend to the end effector 404, and selectiveactuation of those drive members may cause the end effector 404 toactuate (operate). In the illustrated embodiment, actuating the endeffector 404 may comprise closing and/or opening the second jaw 412relative to the first jaw 410 (or vice versa), thereby enabling the endeffector 404 to grasp (clamp) onto tissue. In addition, once tissue isgrasped or clamped between the opposing jaws 410, 412, actuating the endeffector 404 may further comprise “firing” the end effector 404, whichmay refer to causing a cutting element or knife (not visible) to advancedistally within a slot 414 defined in the second jaw 410. As it movesdistally, the cutting element may transect any tissue grasped betweenthe opposing jaws 410, 412. Moreover, as the cutting element advancesdistally, a plurality of staples contained within the staple cartridge(i.e., housed within the first jaw 410) may be urged (cammed) intodeforming contact with corresponding anvil surfaces (e.g., pockets)provided on the second jaw 412. The deployed staples may form multiplerows of staples that seal opposing sides of the transected tissue.

In some embodiments, the surgical tool 400 may be configured to applyenergy to tissue, such as radio frequency (RF) energy. In such cases,actuating the end effector 404 may further include applying energy totissue grasped or clamped between two opposing jaws to cauterize or sealthe captured tissue, following which the tissue may be transected.

In some embodiments, the surgical tool 400 may further include a manualclosure device 416 accessible to a user on the exterior of the drivehousing 408. As illustrated, the manual closure device 416 may comprisea knob that may be grasped by the user. The manual closure device 416may be operatively coupled to various gears and/or drive members withinthe drive housing 408 to allow a clinician to manually open and closethe jaws 410, 412. In some cases, a clinician may be able to fully clampand fully unclamp the jaws 410, 412 with the manual closure device 416.The manual closure device 416 may be particularly useful to a clinicianwhen the surgical tool 400 is detached from a surgical robot, sincehaving the capability to open and close the jaws 410, 412 may eliminatethe need to place inadvertent stress on internal drive members orcomponents. In the event that a clinician desires to manually open thejaws 410, 412 when the surgical tool 400 is still attached to a surgicalrobot, the clinician can rotate the manual closure device 416 in anattempt to open the end effector 404.

FIG. 6 depicts a bottom view of the drive housing 408, according to oneor more embodiments. As illustrated, the drive housing 408 may include atool mounting portion 602 used to operatively couple the drive housing408 to a tool driver 604. The tool driver 604 may be the same as orsimilar to the tool drivers 308 of FIG. 3 , and may thus be operable inconjunction with the robotic manipulator 104 of FIGS. 1 and 3 . Mountingthe drive housing 408 to the tool driver 604 places the drive housing408 in communication with a computer system 606, which may communicatewith or otherwise form part of the master controllers 102 a,b (FIG. 1 ).The computer system 608 monitors and directs operation of the drivehousing 408 via operation of the tool driver 604, thus enabling a user(e.g., the clinicians 112 a,b of FIG. 1 ) to control operation of thedrive housing 408 by working through the master controller 102 a,b

The tool mounting portion 602 includes and otherwise provides aninterface that mechanically, magnetically, and/or electrically couplesthe drive housing 408 to the tool driver 604. In at least oneembodiment, the tool mounting portion 602 couples the drive housing 408to the tool driver 604 via a sterile barrier (not shown). Asillustrated, the interface of the tool mounting portion 602 can includeand support a plurality of inputs, shown as drive inputs 608 a, 608 b,608 c, 608 d, 608 e, and 608 f. Each drive input 608 a-f may comprise arotatable disc or puck configured to align (mate) with and couple to acorresponding driver 610 a, 610 b, 610 c, 610 d, 610 e, and 610 f of thetool driver 604. Each drive input 608 a-f and corresponding driver 610a-f provide or define one or more matable surface features 612 and 614,respectively, configured to facilitate mating engagement between theopposing surface features 612, 614 such that movement (rotation) of agiven driver 610 a-f correspondingly moves (rotates) the associateddrive input 608 a-f.

Each driver 610 a-f of the tool driver 604 may include or otherwisecomprise a motor 616 configured to actuate the corresponding driver 610a-f, and actuation of a given driver 610 a-f correspondingly causesactuation of the mated drive input 608 a-f, which facilitates operationof the mechanics of the drive housing 408. More specifically, actuationof the motors 616 may cause rotational movement of the correspondingdriver 610 a-f, which, in turn, rotates the associated drive input 608a-f. Each motor 616 may be in communication with the computer system 606and, based on input signals provided by a user (e.g., a surgeon), thecomputer system 606 may selectively cause any of the motors 616 toactuate and thereby drive the corresponding driver 610 a-f.

In some embodiments, actuation of the first drive input 608 a via thefirst driver 610 a may control rotation of the shaft 402 about itslongitudinal axis A₁. Depending on the rotational direction of the firstdrive input 608 a, the shaft 402 can be rotated clockwise orcounter-clockwise, thus correspondingly rotating the end effector 404(FIG. 4 ) in the same direction. Actuation of the second and third driveinputs 608 b,c via the second and third drivers 610 b,c, respectively,may control articulation of the end effector 404 at the wrist 406 (FIG.4 ). Actuation of the fourth and fifth drive inputs 608 d,e via thefourth and fifth drivers 610 d,e, respectively, may cause an outerportion of the shaft 402 (referred to herein as a “closure tube”) toadvance and retract, which closes and opens the jaws 410, 412 (FIG. 4 ).Lastly, actuation of the sixth drive input 608 f via the sixth driver610 f may cause the end effector 404 to fire, which may entail distaldeployment of a cutting element to transect tissue grasped by the jaws410, 412 and simultaneous deployment of staples contained within thestaple cartridge housed within the first jaw 410.

The tool mounting portion 602 may further include one or more electricalconnectors 618 (two shown) configured to mate with correspondingelectrical connections 620 (two shown) provided by the tool driver 604to facilitate communication between the drive housing 408 and the tooldriver 604. Alternately, the drive housing 408 can wirelesslycommunicate with the tool driver 604, such as through a near fieldcommunication connection. The drive housing 408 may further house orotherwise include an internal computer 622 that may include a memory 624and/or a microprocessor 626. The memory 624 may include one or moredatabases or libraries that store data relating to the drive housing 408and, more particularly, to the surgical tool 400 (FIG. 4 ). In someembodiments, the memory 624 may include non-transitory,computer-readable media such as a read-only memory (ROM), which may bePROM, EPROM, EEPROM, or the like. Mating the drive housing 408 to thetool driver 604 places the internal computer 622 in communication withthe computer system 606.

The computer system 606 may be programmed and otherwise configured tomonitor operation of the surgical tool 400 (FIG. 4 ) using varioussensors and/or electromechanical devices, collectively referred toherein as “monitoring devices.” Each monitoring device may be designedto monitor one or more operational parameters of the surgical tool 400and report measured operational parameters to the computer system 606for processing. The computer system 606, for example, may be incommunication with one or more torque sensors 628 and/or one or morerotary encoders 630, each of which may be characterized as a monitoringdevice designed to monitor operational parameters of the surgical tool400. The torque sensors 628, for instance, may be configured to monitortorque, and the rotary encoders 630 may be configured to monitor motion(rotational or linear).

The torque sensors 628 and the rotary encoders 630 may be incorporatedinto the motors 616 of some or all of the drivers 610 a-f, but couldalternatively be operatively coupled to one or more of the drive inputs608 a-f. The torque sensors 628 may be configured to measure thereal-time torque loading on the motors 616, which corresponds to thetorque loading assumed by the drivers 610 a-f and/or the drive inputs608 a-f. The rotary encoders 630 may measure the rotational motion oroutput of the motors 616, which corresponds to the rotational motion ofthe drivers 610 a-f and/or the drive inputs 608 a-f. Monitoring torqueloading and rotational motion of the motors 616 may help determine ifthe surgical tool 400 is operating in accordance with the commandsprovided by the computer system 606.

Referring to FIGS. 7A and 7B and FIGS. 8A and 8B, illustrated areexposed isometric views of the interior of the drive housing 408,according to one or more embodiments. The upper portion of the drivehousing 408 is omitted in FIGS. 7A-7B to allow viewing of the internalworking components and parts, and both the upper and lower portions ofthe drive housing 408 are omitted in FIGS. 8A-8B to allow viewing of theinternal working components and parts. In addition, several componentparts that would otherwise be included within the drive housing 408 areomitted in FIGS. 7A-7B and 8A-8B to simplify the figures and enablediscussion of the depicted component parts.

Referring first to FIG. 7A, a first drive shaft 702 a is coupled to thefirst drive input 608 a (FIG. 6 ) such that actuation and rotation ofthe first drive input 608 a correspondingly rotates the first driveshaft 702 a. A helical drive gear 704 is coupled to the first driveshaft 702 a and rotates as the first drive shaft 702 a rotates. Thehelical drive gear 704 intermeshes with a helical driven gear 706, whichis operatively coupled to the shaft 402 and, more particularly, to aninner grounding member or shaft 708 that forms part of the shaft 402.The inner grounding shaft 708 extends concentrically within an outerportion of the shaft 402 referred to herein as the “closure tube.”Accordingly, actuation of the first drive input 608 a drives the firstdrive shaft 702 a and correspondingly drives the inner grounding shaft708 to rotate the shaft 402 about the longitudinal axis A₁.

A second drive shaft 702 b may be coupled to the second drive input 608b (FIG. 6 ) such that actuation and rotation of the second drive input608 b correspondingly rotates the second drive shaft 702 b. In someexamples, a drive train or gearing may be provided to adjust themechanical advantage output from one or more motors of the roboticmanipulator (not illustrated). For example, if the second driver 610 b(FIG. 6 ) outputs relatively low torque, one or more intermeshed gearsmay be utilized to increase the torque imparted by the second driver 610b on the drive shaft 702 b. As best exemplified in FIGS. 8A-8B, a spurgear 709 a is attached and keyed to the second drive shaft 702 b suchthat the spur gear 709 a rotates in unison with drive shaft 702 b. Also,a compound pinion gear 710 a is rotatably attached to the second driveshaft 702 b, such that the compound pinion gear 710 a is rotatable aboutand relative to the second drive shaft 702 b. As illustrated, thecompound pinion gear 710 a includes a first pinion gear 711 a and asecond pinion gear 713 a that are rigidly connected together such thatthey rotate together about the second drive shaft 702 b. The secondpinion gear 713 a of the compound pinion gear 710 a intermeshes with afirst driven rack 712 a such that, as the compound pinion gear 710 a isrotated in a first rotational direction, the first driven rack 712 acorrespondingly translates in a first longitudinal direction; and, asthe compound pinion gear 710 a is rotated in a second rotationaldirection, the first driven rack 712 a correspondingly translates in asecond longitudinal direction opposite the first longitudinal direction.

In addition, an idler assembly 715 a (FIGS. 8A-8B) is provided totransfer rotation of the second drive shaft 702 b to the compound piniongear 710 a and thereby effectuate translation of the first driven rack712 a in the first or second longitudinal direction. In the illustratedexample, the idler assembly 715 a is a compound gear having a firstidler 717 a and a second idler 719 a that is rigidly connected to thefirst idler 717 a such that they rotate together in unison. Here, thefirst idler 717 a meshes with the spur gear 709 a that is keyed to thesecond drive shaft 702 b, and the second idler 719 a meshes with thefirst pinion gear 711 a of the compound pinion gear 710 a to therebydrive the first driven rack 712 a. Thus, the second driver 610 b (FIG. 6) rotates the second drive input 608 b, which in turn rotates the seconddrive shaft 702 b and the spur gear 709 a connected thereto. The spurgear 709 a imparts rotation to the first idler 717 a of the idlerassembly 715 a, which in turn also imparts rotation on the second idler719 a thereof as it is keyed to the first idler 717 a. The second idler719 a of the idler assembly 715 a imparts rotation on the first piniongear 711 a of the compound pinion gear 710 a, which in turn also impartsrotation on the second pinion gear 713 a of the compound pinion gear 710a as it is keyed to the first pinion gear 711 a. As described above,such rotation of the second pinion gear 713 a causes translation of thefirst drive rack 712 a.

The illustrated drive train transferring power between the second driver610 b (FIG. 6 ) and the first driven rack 712 a is configured with acumulative gear ratio that increases the torque that the compound piniongear 710 a exerts on the first drive rack 712 a beyond what is initiallyapplied to the drive input 608 b by the second driver 610 b. Inparticular, because the spur gear 709 a is smaller (i.e., less teeth)than the first idler 717 a with which it meshes and because the secondidler 719 a is smaller (i.e., less teeth) than the first pinion gear 711with which it meshes, the torque acting on the compound pinion gear 710a that drives the first drive rack 712 a is significantly larger thanthe torque initially applied on the second drive shaft 702 b via thesecond driver 610 b.

The first driven rack 712 a includes a first fork 714 a matable with afirst articulation yoke 716 a. More specifically, the first fork 714 ais configured to be received within an annular slot 718 a (FIGS. 7A and8B) defined in the first articulation yoke 716 a, which allows the firstarticulation yoke 716 a to rotate about the longitudinal axis A₁ as theinner grounding shaft 708 rotates. Moreover, engagement between thefirst fork 714 a and the annular slot 718 a allows the first driven rack712 a to drive the first articulation yoke 716 a along the longitudinalaxis A₁ (distally or proximally) as acted upon by rotation of the seconddrive shaft 702 b. The first articulation yoke 716 a may be coupled to afirst drive member 720 a, which extends distally to the wrist 406 (FIG.4 ). As illustrated, the first drive member 720 a is arranged within acorresponding slot defined in the inner grounding shaft 708, such thatthe inner grounding shaft 708 guides the first drive member 720 a asthey extend distally together to the wrist 406 (FIG. 8 ). Axial movementof the first articulation yoke 716 a along the longitudinal axis A₁correspondingly moves the first drive member 720 a, which causes thewrist 406 and the end effector 404 (FIG. 4 ) to articulate.

A third drive shaft 702 c is coupled to the third drive input 608 c(FIG. 6 ) such that actuation and rotation of the third drive input 608c correspondingly rotates the third drive shaft 702 c. Similar to thedescription of the second drive shaft 702 b coupled to the second driveinput 608 b, a drive train or gearing may be provided to adjustmechanical advantage and thus vary the torque or speed initially appliedby the third driver 610 c (FIG. 6 ) to the third drive shaft 702 c. Inthe illustrated example, a spur gear 709 b is attached and keyed to thethird drive shaft 702 c such that the spur gear 709 b rotates in unisonwith third drive shaft 702 c. A compound pinion gear 710 b is rotatablyattached to the third drive shaft 702 c such that the compound piniongear 710 b may rotate about and relative to the third drive shaft 702 c.As illustrated, the compound pinion gear 710 b includes a first piniongear 711 b and a second pinion gear 713 b that are rigidly connectedtogether such that they rotate together about the third drive shaft 702c. The second pinion gear 713 b of the compound pinion gear 710 bintermeshes with a second driven rack 712 b such that rotating thecompound pinion gear 710 b in a first rotational directioncorrespondingly translates the second driven rack 712 b in a firstlongitudinal direction. Rotating the compound pinion gear 710 b in asecond rotational direction correspondingly translates the second drivenrack 712 b in a second longitudinal direction opposite the firstlongitudinal direction.

In addition, an idler assembly 715 b is provided to transfer rotation ofthe third drive shaft 702 c to the compound pinion gear 710 b andthereby effectuate translation of the second driven rack 712 b in thefirst or second longitudinal direction. In the illustrated example, theidler assembly 715 b is a compound gear having a first idler 717 b and asecond idler 719 b that is rigidly connected to the first idler 717 bsuch that they rotate together in unison. Here, the first idler 717 bmeshes with the spur gear 709 b that is keyed to the third drive shaft702 c, and the second idler 719 b meshes with the first pinion gear 711b of the compound pinion gear 710 b to thereby drive the second drivenrack 712 b. Thus, the third driver 610 c (FIG. 6 ) rotates the thirddrive input 608 c, which in turn rotates the third drive shaft 702 c andthe spur gear 709 b connected thereto. The spur gear 709 b impartsrotation to the first idler 717 b of the idler assembly 715 b, which inturn also imparts rotation on the second idler 719 b thereof as it iskeyed to the first idler 717 b. The second idler 719 b of the idlerassembly 715 b imparts rotation on the first pinion gear 711 b of thecompound pinion gear 710 b, which in turn also imparts rotation on thesecond pinion gear 713 b of the compound pinion gear 710 b as it iskeyed to the first pinion gear 711 b. As described above, such rotationof the second pinion gear 713 b causes translation of the first driverack 712 b. The illustrated drive train transferring power between thethird driver 610 c and the second driven rack 712 b is configured with acumulative gear ratio that results in increased output torque acting onthe compound pinion gear 710 b and thereby exerted on the second driverack 712 b beyond what is initially applied to the third drive input 608c by the third driver 610 c.

The second driven rack 712 b includes a second fork 714 b matable with asecond articulation yoke 716 b. More particularly, the second fork 714 bis configured to be received within an annular slot 718 b defined in thesecond articulation yoke 716 b, which allows the second articulationyoke 716 b to rotate about the longitudinal axis A₁ as the innergrounding shaft 708 rotates. Moreover, engagement between the secondfork 714 b and the annular slot 718 b allows the second driven rack 712b to drive the second articulation yoke 716 b along the longitudinalaxis A₁ (distally or proximally) as acted upon by rotation of the thirddrive shaft 702 c. The second articulation yoke 716 b may be coupled toa second drive member 720 b (FIG. 7A), which extends distally to thewrist 406 (FIG. 4 ). The second drive member 720 b is arranged within acorresponding slot defined in the inner grounding shaft 708, such thatthe inner grounding shaft 708 guides the second drive member 720 b asthey extend distally together to the wrist 406 (FIG. 8 ). Axial movementof the second articulation yoke 716 b along the longitudinal axis A₁correspondingly moves the second drive member 720 b, which causes thewrist 406 and the end effector 404 (FIG. 4 ) to articulate.

Accordingly, axial movement of the first and second articulation yokes716 a,b, along the longitudinal axis A₁ cooperatively actuates the drivemembers 720 a,b and, thereby, articulates the end effector 404 asfurther described herein with reference to FIGS. 9A-9B and 10A-10B. Inat least one embodiment, the first and second articulation yokes 716 a,bprotagonistically operate such that one of the articulation yokes 716a,b pulls one of the drive members 720 a,b proximally while the otherarticulation yoke 716 a,b pushes the other drive member 720 a,bdistally. In some embodiments, however, the first and secondarticulation yokes 716 a,b may be operated independently without theother being operated (affected), for example, they may operateantagonistically where one reduces the force effect of another. Inantagonistic operation, one of the articulation yolks 716 a,b pulls (orpushes) the drive member 720 a,b associated therewith proximally (ordistally) with a first force while the other one of the articulationyolks 716 a,b pulls (or pushes) the drive member 720 a,b associatedtherewith proximally (or distally) with a second force, where the firstforce is larger than the second force such that the first force canovercome the second force, as well as the internal losses of the device(i.e., friction) and loads imparted on the end effector 404 via theexternal environment, thereby ensuring that the articulation yolk 716a,b providing the first force moves proximally (or distally) while thearticulation yolk 716 a,b providing the second force moves distally (orproximally). As described below, the computer system 606 (FIG. 6 ) maybe configured to control the drivers 610 b,c (FIG. 6 ) that drive thedrive inputs 608 b-c and interconnected drive shafts 702 b-c to therebysynchronize actuation of the articulation yokes 716 a,b.

A fourth drive shaft 702 d (FIG. 7A) and a fifth drive shaft 702 e (FIG.7B) may be coupled to the fourth and fifth drive inputs 608 d,e (FIG. 6), respectively, such that actuation and rotation of the fourth andfifth drive inputs 608 d,e correspondingly rotates the fourth and fifthdrive shafts 702 d,e. Rotation of the fourth and fifth drive shafts 702d,e may cause a portion of the shaft 402 to advance or retract. Morespecifically, the outer portion of the shaft 402 may comprise a closuretube 722 that is axially translated to move the jaws 410, 412 (FIG. 4 )between open and closed positions. As illustrated, each drive shaft 702d,e has a spur gear 724 attached thereto, and both spur gears 724 arepositioned to mesh with a primary drive gear 725 mounted to a closureyoke 726.

The closure yoke 726 is rotatably mounted to the closure tube 722 butfixed axially thereto. This allows the closure tube 722 to rotate as theinner grounding shaft 708 rotates, but also allows the closure yoke 726to advance or retract the closure tube 722. A projection 727 (FIG. 8A)extends from or is otherwise coupled to the closure yoke 726, and theprojection interacts with a camming surface or slot defined within theprimary drive gear 725 to facilitate axial movement of the closure yoke726. Accordingly, rotating the spur gears 724 causes the primary drivegear 725 to rotate, which correspondingly causes the closure yoke 726and the interconnected closure tube 722 to axially translate.

The primary drive gear 725 may also be operatively coupled to the manualclosure device 416 arranged on the exterior of the drive housing 408. Asillustrated, the manual closure device 416 may include a drive gear 728that intermeshes with a driven gear 729 mounted to the primary drivegear 725. Consequently, a user can grasp and rotate the manual closuredevice 416 to correspondingly rotate the primary drive gear 725 andthereby drive the drive gear 728 against the driven gear 729 to move theclosure yoke 426 distally and proximally to close and open the jaws 410,412 (FIG. 4 ), as generally described above. In one example, of theprimary drive gear 725 is intermeshed between the spur gears 724 andcomprises a central aperture that rotatably mounts the primary drivegear 725 within the drive housing 408 (FIGS. 7A-7B) relative to the spurgears 724. A spiral cam slot is defined in the primary drive gear 725and the projection 727 (FIG. 8A) of the closure yoke 726 (FIGS. 7A-7B)is received therein. The primary drive gear 725 is rotatable about anaxis extending through the central aperture as acted upon by the spurgears 724. As the primary drive gear 725 rotates, the projection followsthe spiral cam slot, and the curvature of the spiral cam slot urges theinterconnected closure yoke 726 to translate longitudinally relative tothe primary drive gear 725. When the closure yoke 726 moves distally,the closure tube 722 (FIGS. 7A-7B) correspondingly moves in the distaldirection and causes the jaws 410, 412 (FIG. 4 ) to close. In contrast,when the closure yoke 726 moves proximally, the closure tube 722correspondingly moves in the proximal direction and causes the jaws 410,412 to open.

FIGS. 9A and 9B illustrate exposed bottom views of the surgical tool400, according to one or more embodiments. Much of the gearing andactuation mechanisms described above are depicted, but the entirety ofthe drive housing 408 and the closure tube 722 of the shaft 402 areomitted in FIGS. 9A-9B to allow viewing of the internal workingcomponents and parts utilized to articulate the drive members 720 a,band the wrist 406. In addition, several component parts that wouldotherwise be included within the drive housing 408 are omitted in thesefigures to simplify the figures and enable discussion of the depictedcomponent parts.

With reference to FIG. 9A, the inner grounding shaft 708 extendsdistally within the shaft 402 and is connected to the wrist 406. Thedrive members 720 a,b extend distally towards the wrist 406 withincorresponding slots 802 a,b defined within the inner grounding shaft708. The corresponding slots 802 a,b may be provided on opposite sidesof the inner grounding shaft 708, or may be defined elsewhere about theinner grounding shaft 708 in other examples. As described below,movement of the drive members 720 a,b articulates the wrist 406. Also,the inner grounding shaft 708 is configured to effect rotation of thewrist 406 about the longitudinal axis A₁, even when the wrist 406 isarticulated to an angularly offset position relative to the longitudinalaxis A₁.

In the illustrated example, a locking or grounding recess (obscured fromview) is formed into a bottom side of the distal end of the innergrounding shaft 708, and the grounding recess defines a pair of lockingtabs 804 a,b configured to interlock with other componentry of the wrist406. Here, a base 806 of the wrist 406 is integrally secured within thegrounding recess of the inner grounding shaft 708 via the locking tabs804 a,b such that the inner grounding shaft 708 carries the wrist 406 asit rotates about the longitudinal axis A₁ upon actuation of the firstdrive input 608 a. In addition, the slots 802 a,b extend through thegrounding recess and the locking tabs 804 a,b, with lower boundary ofthe slots 802 a,b being defined by an upper surface of the base 806, asdescribed below.

The wrist 406 further includes an articulation member 808 to which theend effector 404 may be mounted. The articulation member 808 is coupledto the base 806 and the drive members 720 a,b, such that movement of thedrive members 720 a,b articulates the articulation member 808 relativeto the base 806. Thus, the wrist 406 and the end effector 404 extendingdistally therefrom may be angularly offset via movement of the drivemembers 720 a,b.

In FIG. 9B the inner grounding shaft 708 has been removed. Asillustrated, the drive members 720 a,b are interconnected at theirdistal ends via a third link member, described herein with reference toFIG. 10B and referred to herein as a “distal link.” Thus, the drivemembers 720 a,b and the distal link together comprise a linkageconfigured to articulate the articulation member 808 relative to thebase 806 in a plane parallel to the longitudinal axis A₁. With thisconfiguration, the drive members 720 a,b translate antagonisticallywithin their corresponding slots 802 a,b (FIG. 9A) along thelongitudinal axis A₁, such that as the first drive member 720 a movesdistally the second drive member 702 b moves proximally, and vice versa.More specifically, distal movement of the first drive member 720 a actson the articulation member 808 and causes the articulation member 808 torotate clockwise and thereby push the second drive member 720 bproximally. Thus, the first drive member 720 a moves distally as thesecond drive member 720 b moves proximally, thereby causing the wrist406 to articulate in the plane such that it is angularly offset at anon-zero angle relative to the inner grounding shaft 708. As mentionedabove, the wrist 406 is also configured to rotate with the innergrounding shaft 708 about the longitudinal axis A₁, and thereby rotatethe plane in which the articulation member 808 articulates (360° aboutthe longitudinal axis A₁).

FIG. 10A illustrates a bottom view of the wrist 406, according to one ormore embodiments. As illustrated, the base 806 is attached to the innergrounding shaft 708 and arranged within the closure tube 722. Here, theclosure tube 722 includes a distal clevis 1002 having a pair ofapertures 1004. In addition, a closure link 1006 having a pair of pins1008, 1010 is provided and, when the base 806 and the inner groundingshaft 708 are arranged within the closure tube 722, the first pin 1008of the closure link 1006 is received within one of the apertures 1004 inthe distal clevis 1002. The closure link 1006 is utilized to transmitclosure action around the articulation joint. For example, the closurelink 1006 may transmit the closure load or translation of the closuretube 722 to a closure ring (not illustrated) that may be coupled to thesecond pin 1010 of the closure link 1006, which pulls or pushes theupper jaw (anvil) open or closed. Also, the articulation member 808 isable to rotate about an articulation axis A₃ that, in the illustratedexample, is shown extending through the second pin 1010 of the closurelink 1006.

FIG. 10B illustrates an exploded isometric view of the wrist 406 of FIG.10A. As mentioned, the grounding member 708 includes a grounding recessconfigured to rigidly secure the base 806 thereto. As illustrated, theinner grounding shaft 708 includes a pair of grounding recesses 1012,1014 formed into a distal end of the inner grounding shaft 708. Asshown, the grounding recesses 1012, 1014 define or provide the lockingtabs 804 a,b configured to engage the base 806 and inhibit relativerotation there-between. In the illustrated example, the base 806includes a pair of notches 1016 a and 1016 b configured to receive thelocking tabs 804 a,b, and the pair of notches 1016 a,b define a proximallocking flange 1018 configured to be received within the groundingrecess 1014 when assembled. When the base 806 is assembled on the innergrounding shaft 708, with locking tabs 804 a,b extending into thenotches 1016 a,b and the proximal locking flange 1018 extending into thegrounding recess 1014, the base 806 will rotate together with the innergrounding shaft 708 as described above.

Also, the slots 802 a,b are illustrated extending longitudinally alongthe inner grounding shaft 708. The slots 802 a,b are each defined orbounded by an upper surface 1020 of the inner grounding shaft 708 and alower surface 1022 of the inner grounding shaft 708. In the illustratedexample, the upper surfaces 1020 are substantially continuous along thelength of the inner grounding shaft 708, but the lower surfaces 1022 arediscontinuous or broken due to the grounding recesses 1012, 1014. Asillustrated, the lower surfaces 1022 are absent along distal portions ofthe inner grounding shaft 708 corresponding with the grounding recess1012, and the grounding recess 1014 interposes proximal portions of thelower surfaces 1022 and a distal portion of the lower surfaces 1022extending along the locking tabs 804 a,b.

The base 806, however, includes lower surfaces 1024 that define or boundportions of the slots 802 a,b at locations corresponding with thegrounding recesses 1012, 1014. As illustrated, the lower surfaces 1024of the base 806 extend along the proximal locking flange 1018 of thebase 806, but are discontinuous and broken via the notches 1016 a,b, andthen extend distally therefrom. Thus, when the base 806 is assembled onthe inner grounding shaft 708, the slots 802 a,b are bounded by theupper and lower surface 1020, 1022 of the inner grounding shaft 708along proximal portions thereof and along the locking tabs 804 a,b;whereas, the slots 802 a,b are bounded by the upper surface 1020 of theinner grounding shaft 708 and the lower surface 1024 of the base 806 atlocations along the inner grounding shaft 708 that correspond with thegrounding recesses 1012, 1014.

The base 806 has an upper portion 1026 and a lower portion 1028. Asillustrated, the lower surfaces 1024 define an upper surface of thelower portion 1028 of the base 806 and thereby partition the upperportion 1026 from the lower portion 1028. The base 806 also includes anarticulation portion 1030 located at a distal end of the base 806. Thearticulation portion 1030 is configured to receive the articulationmember 808 and permit rotation of the articulation member 808 relativeto the base 806. As illustrated, the articulation portion 1030 includesan extension member 1032 distally extending from the upper portion 1026of the base 806, and a pivot shaft 1034 oriented on the articulationaxis A₃ for receiving the articulation member 808. As shown, the pivotshaft 1034 extends downward from the upper portion 1026 towards thelower portion 1028. In addition, the articulation portion 1030 includesa recess 1036 formed into the lower portion 1028 at the distal end ofthe base 806, which is configured to receive the articulation member 808and permit rotation thereof within the recess 1036. As illustrated, thepivot shaft 1034 extends downward into the recess 1036 and a distal face1038 of the lower portion 1028 includes a curvature that correspondswith a curvature of the articulation member 808, as described below.

In addition, a recess 1040 is formed into a distal end of the extensionmember 1032 for receiving the distal link interconnecting the drivemembers 720 a,b as described below. The recess 1040 is defined by asliding surface 1042 on which the distal link may slide and an upperdistal face 1044 of the extension member 1032 on which the distal linkmay articulate or pivot, and the upper distal face 1044 may include acurvature that corresponds with a curvature of the distal link. Also inthe illustrated example, a lower distal face 1046 of the extensionmember 1032 includes a curvature that corresponds with a curvature ofthe articulation member 808.

The articulation member 808 includes an end effector mounting portion1050 at a distal end thereof and a coupling portion 1052 proximallyextending from the end effector mounting portion 1050. The end effectormounting portion 1050 is configured to receive an end effector, forexample, the end effector 404 of the surgical tool 400 illustrated inFIG. 4 . The coupling portion 1052 is configured to be received androtatably coupled within the recess 1036 in the distal end of the base806, such that it may articulate relative to the base 806 when actuatedby the drive members 720 a,b.

The articulation member 808 includes an aperture 1054 extending throughthe coupling portion 1052. The aperture 1054 is configured to receivethe pivot shaft 1034 of the base 806 and therefore is oriented along thearticulation axis A₃ when the articulation member 808 is assembled onthe base 806. When the base 806 and the articulation member 808 areassembled together with the pivot shaft 1034 extending through theaperture 1054, the coupling portion 1052 of the articulation member 808is disposed within the recess 1036 defined in the lower portion 1028 thebase 806 such that the articulation member 808 may rotate about thearticulation axis A₃ relative to the base 806. Here, a proximal face1056 of the coupling portion 1052 abuts the distal face 1038 of the base806 and thus includes a curvature that corresponds with the curvature ofthe distal face 1038 of the lower portion 1028 as described above. Also,a proximal face 1058 of the end effector mounting portion 1050 abuts thelower distal face 1046 of the extension member 1032 when thearticulation member 808 is assembled on the base 806. Thus, the proximalface 1058 includes a curvature that corresponds with the curvature ofthe lower distal face 1046 of the extension member 1032 and, in someexamples, the curvature of the proximal face 1058 is defined by a radiusequal to the swept distance that the extension member 1032 extendsbeyond the articulation axis A₃ (i.e., distance between the articulationaxis A₃ and the lower distal face 1046).

The articulation member 808 includes a pair of drive pins 1060 a,bconfigured to be engaged by the drive members 720 a,b. Here, the drivepins 1060 a,b extend upward from an upper surface 1062 of the couplingportion 1052. When the base 806 and the articulation member 808 areassembled together, with the coupling portion 1052 rotatably disposedwithin the recess 1036 and with the pivot shaft 1034 extending throughthe aperture 1054, the upper surface 1062 of the coupling portion 1052is substantially aligned or planar with the lower surfaces 1024 of thebase 806 such that the drive members 720 a,b may slide unobstructedthereon. Also, the drive pins 1060 a,b extend upward from the uppersurface 1062 of the coupling portion 1052 a sufficient distance suchthat they may be engaged by the drive members 720 a,b when riding in theslots 802 a,b.

In the illustrated example, the drive pins 1060 a,b extend upward fromthe upper surface 1062 and each terminate at a pin end 1064 a,b. Here,the pin ends 1064 a,b are cylindrical members extending upward from thedrive pins 1060 a,b and have a reduced diameter from the drive pins 1060a,b from which they coaxially extend. The pin ends 1064 a,b each definea surface 1066 that is substantially aligned or planar with an uppersurface 1068 of the base 806 extending onto the extension member 1032thereof. Thus, when the base 806 and the articulation member 808 areassembled together, the drive pins 1060 a,b extend upward from thesliding surface 1042 and the pin ends 1064 a,b extend upward from thedrive pins 1060 a,b such that the surfaces 1066 of the pin ends 1064 a,bare oriented parallel with the upper surface 1068 of the base 806. Inother examples, however, the drive pins 1060 a,b and/or the pin ends1064 a,b may extend upward at different heights, and in some examplesthe drive pins 1060 a,b do not include pin ends 1064 a,b such that thedrive pins 1060 a,b are cylinder shaped members having a uniformdiameter.

FIG. 10B also illustrates the drive members 720 a,b, each of whichprovides a distal end 1070 a and 1070 b, respectively, configured toengage the articulation member 808. A drive pin aperture 1072 isprovided at the distal end 1070 a,b of each drive member 720 a,b and isconfigured to receive the drive pins 1060 a,b of the articulation member808 when the articulation member 808 is assembled on the base 806 and toallow the drive pins 1060 a,b to translate laterally within thecorresponding aperture 1072 when the drive members 720 a,b are actuatedto articulate the wrist 406. The drive pin apertures 1072 may havevarious geometries, for example, rectangular or square shape geometries.In the illustrated example, the drive pin apertures 1072 have agenerally rectangular shape with rounded corners, which allows relativetranslation of the drive pins 1060 a,b during articulation. Regardlessof their shape, the drive pin apertures 1072 are sized to receive thedrive pins 1060 a,b or at least a portion of the drive pins 1060 a,b.

Also, the distal ends 1070 a,b of the drive members 720 a,b areconstrained together via a distal link 1074. As mentioned above, thedrive members 720 a,b and the distal link 1074 together comprise alinkage that articulates the articulation member 808. The distal link1074 includes a pair of wings 1076 a and 1076 b that correspond with thedistal ends 1070 a,b of the drive members 720 a,b, and each wing 1076a,b includes an aperture 1078 configured to receive one of the drivepins 1060 a,b or a portion thereof. In the illustrated example, theapertures 1078 are circular shaped holes configured to receive the pinends 1064 a,b of the drive pins 1060 a,b. In examples where the drivepins 1060 a,b do not include reduced diameter pin ends 1064 a,b, theapertures 1078 may be circular shaped holes sized to receive the drivepins 1060 a,b. The apertures 1078 may have various other shapes,however. In some examples, the apertures 1078 are shaped to correspondwith the drive pin apertures 1072 of the drive members 720 a,b. Inaddition, the distal link 1074 includes a bridge portion 1080interconnecting the wings 1076 a,b, and the bridge portion 1080 includesan interior pivot surface 1082 configured to engage and pivot on theupper distal face 1044 of the extension member 1032 (of the base 806).Here, the pivot surface 1082 includes a curvature that corresponds withthe curvature of the upper distal face 1044.

When assembled, the drive pins 1060 a,b couple the drive members 720 a,bto the distal link 1074. For example, the drive members 720 a,b extenddistally in the slots 802 a,b along the lower surfaces 1022,1024 and thedistal ends 1070 a,b extend over the coupling portion 1052 of thearticulation member 808, with the lower portions of the drive pins 1060a,b extending upward into the apertures 1072 in the drive members 720a,b. Also, the distal link 1074 is arranged in the recess 1042 of thebase 806, with the bridge portion 1080 disposed on the sliding surface1042 and the pivot surface 1082 abutting the upper distal face 1044,such that the pin ends 1064 a,b of the drive pins 1060 a,b extend upwardthrough the apertures 1078 of the distal link 1074. Translation of thedrive members 720 a,b pushes and pulls on the drive pins 1060 a,b of thearticulation member 808, thereby rotating the articulation member 808about the articulation axis A₃. Thus, the articulation member 808 may berotated about the articulation axis A₃, which thereby articulates thewrist 406, via activation of the drivers 610 b,c (FIG. 6 ) that engagethe drive inputs 608 b,c (FIG. 6 ).

Referring again to FIGS. 7A and 7B, a sixth drive shaft 702 f is coupledto the sixth drive input 608 f (FIG. 6 ) such that actuation androtation of the sixth drive input 608 f correspondingly rotates thesixth drive shaft 702 f. Rotating the sixth drive shaft 702 f mayadvance and retract a firing rod (not shown) that extends through theshaft 402 to the end effector 404 (FIG. 4 ). The distal end of thefiring rod is operatively coupled to the cutting element (knife) suchthat axial movement of the firing rod correspondingly moves the cuttingelement distally or proximally to transect tissue grasped between thejaws 410, 412 (FIG. 4 ). In some embodiments, distal movement of thefiring rod also deploys the staples, as described above.

A spur gear 730 is coupled to the sixth drive shaft 702 f such thatrotation of the sixth drive shaft 702 f correspondingly rotates the spurgear 730. The spur gear 730 intermeshes with a second spur gear 732,which is attached to a first transfer drive shaft 734. A third spur gear(not visible) is coupled to the first transfer drive shaft 734 andintermeshes with a fourth spur gear 736, which is attached to a secondtransfer drive shaft 738. Finally, an output pinion gear 740 (FIG. 7A)is coupled to the second transfer drive shaft 738 and intermeshes with arack gear 742 of a firing member 744 such that rotation of the outputpinion gear 740 causes axial translation of the firing member 744. Thefiring member 744 may be coupled to the firing rod (not shown) discussedabove. Accordingly, rotation of the sixth drive shaft 702 f will drivethe firing member 744 in axial translation, which correspondingly drivesthe firing rod in the same direction to advance and retract the cuttingelement at the end effector 404 (FIG. 4 ).

As described above, the tool driver 604 (FIG. 6 ) includes one or moredrivers 610 a-f (FIG. 6 ) configured to actuate corresponding driveinputs 608 a-f (FIG. 6 ), and each driver 610 a-f may be powered by acorresponding motor 616 (FIG. 6 ). Mating engagement between the drivers610 a-f and the corresponding drive inputs 608 a-f allow the drivers 610a-f to be activated to impart rotation to the corresponding drive shafts702 a-f extending from the drive inputs 608 a-f. As mentioned, the wrist406 is articulated by driving the second and third drive inputs 608 b,c,which may be individually driven, one at a time, via the second andthird drivers 610 b,c. To increase available torque, however, the driveinputs 608 b,c may be antagonistically driven by both drivers 610 b,c atthe same time.

While controlling articulation of the wrist 406 with the drivers 610 b,cincreases potential torque to accomplish a desired articulation of thewrist 406, simultaneously operating the drivers 610 b,c presentspotential for over-constrained mechanisms, thereby impairing operationof the surgical tool 400. Thus, the robotic surgical system 100 mayinclude the computer system 600 (FIG. 6 ) configured to control andsynchronize operation of the drivers 610 b,c (or any two or more of thedrivers 610 a-f of FIG. 6 ) such that they operate as a single input(i.e., function as a single driver) more efficiently. This may helpprevent over-constraining drive components coupled thereto, such as thedrive inputs 608 b,c (FIG. 6 ), the drive shafts 702 b,c (FIGS. 7A-7B),the articulation yokes 716 a,b (FIGS. 7A-7B), etc.

FIGS. 11A-11C illustrate various example algorithms programmable intothe computer system 600 of FIG. 6 to control operation of the second andthird drivers 610 b,c (FIG. 6 ), according to various embodiments of thepresent disclosure. Each algorithm identifies and operates a “mastermotor,” corresponding to one of the drivers 610 b,c, and a “slavemotor,” corresponding to the other of the drivers 610 b,c. As discussedabove, the second and third drivers 610 b,c are operatively coupled tothe drive inputs 608 b,c (FIG. 6 ) to cause rotation of thecorresponding drive shafts 702 b,c. The algorithms described herein maycomprise software code instructions programmed into the computer system600 to help prevent mechanical binding of the internal drive mechanismswithin the drive housing 408 that are coupled to the drivers 610 b,c.

It should be noted that while the example algorithms are describedherein with respect to operation of the drivers 610 b,c to causerotation of the drive shafts 702 b,c, one or more of the algorithms maybe utilized with respect to any other of the drivers 610 a-f (FIG. 6 ).For example, one or more of the algorithms may alternatively (or inaddition thereto) be configured to control the fifth and sixth drivers610 e,f operatively coupled to the fifth and sixth drive shafts 702 e,dto cause clamping of the jaws 410, 412 (FIG. 4 ).

In FIG. 11A, a first algorithm 1100 a may be configured to control theposition of the “master motor” using feedback to achieve a device targetset by the clinician 112 a. More specifically, the first algorithm 1100a may be configured to directly control the slave current based on themaster current. Here, the target slave current is equal to the actualmaster current output to the “master motor.” In the illustrated example,the second driver 610 b is designated as the “master motor” and thethird driver 610 c is designated as the “slave motor.” The clinician 112a may pinch or manipulate the user input device 203 to effectarticulation of the wrist 406 into a desired orientation or wrist angle.Thus, the clinician 112 inputs a desired orientation or wrist angle forthe wrist 406 into the computer system 600 (FIG. 6 ) via manipulation ofthe user input device 203. Similarly, the clinician 112 a may pinch ormanipulate the user input device 203 to effect movement of either orboth of the jaws 410, 412 (FIG. 4 ) into a desired orientation orclosure angle, and thereby input a desired orientation or closure anglefor the jaws 410, 412 into the computer system 606. By applying thealgorithm 1100 a, the computer system 606 then converts the desiredorientation or wrist agle of the wrist 406 (and/or the desiredorientation or closure angle of the jaws 410, 412, the end-effector 404position target, etc.) into a master motor position target using aformula for the mechanism moving or positioning the wrist 406 (and/orthe jaws 410, 412, etc.). In one example, the formulae are:

${x:R3} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right.}{{gear}{Radius}}}$${{- x}:R4} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right.}{{gear}{Radius}}}$

In these formulae, the “pinRadius” is the distance between a centralaxis of the pivot shaft 1034 (of the base 806) and the central axis ofone of the pins 1060 a,1060 b (of the articulation member 808) asevaluated in a plane in which the wrist 406 articulates, wherein“gearRadius” is the radius of the second pinion gear 713 a,713 b of thecompound pinion gear 710 a,710 b, and the “GearRatio” is of the combinedgear ratio of the spur gear 709 a,709 b, the idler assembly 715 a,715 b,and the first pinion gear 711 a,711 b.

Via the algorithm 1100 a, the computer system 606 (FIG. 6 ) maycontinuously monitor the actual position (e.g., angular position) of the“master motor” relative to the master motor position target, and thensubtracts a master motor actual position from the master motor targetposition to yield a master position error. Based on the algorithm 1100a, the computer system 606 may then supply voltage to the “master motor”through a master or primary control loop depending on the masterposition error, a change in the master position error, and/or anaccumulation of the master position error over time. Meanwhile, themaster position error of the master control loop is fed to a secondaryor slave control loop for the “slave motor.”

In some embodiments, the algorithm 1100 a may utilize a lookup table toconvert the master position error into a slave motor target current, anda feedback controller of the slave control loop monitors a slave motoractual current and modulates voltage supplied to the “slave motor” toachieve the slave motor target current. In doing so, the “master motor”works to achieve the target motor position (corresponding with thedesired orientation or wrist angle of the wrist 406 and/or desiredclosure angle of the jaws 410, 412), with the “slave motor” operating inconcert by helping push or pull internal drive components in the samedirection as urged by the “master motor” rather than acting against orpushing such internal drive components in an opposite direction fromthat urged by the “master motor.” For example, as the second driver 610b causes rotation of the drive shaft 702 b to distally translate thefirst drive member 720 a and thereby articulate the wrist 406, the thirddriver 610 c will assist achieving such desired articulation by causingthe third drive shaft 702 c to rotate and thereby move the second drivemember 720 b proximally. Thus, both the drivers 610 b,c may work inconcert to complementarily cause articulation of the wrist 406 (i.e.,protagonistically), rather than just one of the drivers 610 b,coperating independently with one of the drivers 610 b,c possiblyoff-setting the force output by the other (i.e., antagonistically).

FIG. 11B is a schematic diagram of another algorithm 1100 b that may beprogrammed into the computer system 606 of FIG. 6 . The second algorithm1100 b may be configured to control the slave current based on aproportion of the master current. Here, the target slave current isequal to a proportion of the actual master current output to the “mastermotor.”

FIG. 11C is a schematic diagram of a third algorithm 1100 c that may beprogrammed into the computer system 606 of FIG. 6 . The third algorithm1100 c may be configured to control the slave current based on both aproportion of the master current and direction changes sensed in the“master motor.” More specifically, the “master motor” direction changesare sensed as the master current changes between a positive or negativevalues (and vice versa), and each such direction change generates adecaying current spike that is added to the proportion of the actualmaster current output to the “master motor.” Using exponentiallydecaying current spikes generated after each direction change of the“master motor,” in addition to the proportional master current, helpsthe “slave motor” catch up to the “master motor.”

As described herein, the drivers 610 a-f of FIG. 6 are configured tomate with corresponding drive inputs 608 a-f (FIG. 6 ) to cause rotationof associated drive shafts 702 a-f (FIGS. 7A-7B) connected thereto,which results in various movements of the end effector 404 (FIG. 4 )and/or the wrist 406 (FIG. 4 ). Each drive input 608 a-f may have aneutral or unarticulated position where they do not impart acorresponding movement to the end effector 404 and/or the wrist 406, butthe drive inputs 608 a-f can sometimes be moved from the neutralposition before the tool 400 is coupled to the tool driver 604 (FIG. 6). In some cases, for example, the drive inputs 608 a-f may have beenpreviously actuated out of their neutral positions to cause movement inthe end effector 404 and/or the wrist 406 during prior use. In othercases, or in addition thereto, one or more of the drive inputs 608 a-fmay be rotated out of their neutral positions during sterilization orcleaning.

However, it is important to be able to quickly and accurately return thedrive inputs 608 a-f to the neutral positions during or prior to use. Inorder to ensure that the drivers 610 a-f do not command the drive inputs608 a-f to positions that may cause damage to the surgical tool 400,systems may be provided for accurately “homing” the surgical tool 400 orone or more sub-systems of the surgical tool 400. For example, the driveinputs 608 a-f may have home positions corresponding with knownpositions of the end effector 404 and/or the wrist 406, and homing thesurgical tool 400 may relate the angular position of the drivers 610 a-fand, by extension the drive inputs 608 a-f coupled thereto, to the knownpositions of the end effector 404 and/or the wrist 406. Not only maythis relationship be utilized to inhibit over-actuation (orover-rotation) of the drive inputs 608 a-f that may otherwise causedamage to the surgical tool 400, but this relationship may be utilizedto establish the actual position the end effector 404 and/or the wrist406 in space.

Conventional homing systems often utilize mechanical limit switches andclosely monitor torque output by the drivers 610 a-f to find the homeposition for the drive inputs 608 a-f. To do this however, the drivers610 a-f must be rotated slowly so as to be able to detect torque spikesprior to hitting a hard stop and potentially breaking componentsassociated with the limit switches. This can add a significant amount oftime to a homing sequence, especially when utilizing surgical toolshaving high gear ratios.

According to embodiments of the present disclosure, the robotic surgicalsystem 100 (FIG. 1 ) may include a homing system configured to quicklyreturn (or home) the drive inputs 608 a-f to their neutral positions.The surgical tool 400 (FIG. 4 ) may be manufactured to be installed onthe sterile barrier of the robotic manipulator so that the rotationalposition of the drive inputs 608 a-f are known. For example, the driveinputs 608 a-f may each be keyed to couple to their corresponding driver610 a-f when in a certain rotational position. This permits the homingsystem to identify the relative rotational (angular) position of thedrive inputs 608 a-f when the surgical tool 400 is coupled to the tooldriver 604 (FIG. 6 ) and associate that relative rotational position ofthe drive inputs 608 a-f with a specific cumulative motor position ofthe driver 610 a-f that is known by the homing system.

During manufacture, the surgical tool 400 is calibrated to determine theabsolute rotational value at which each of the drive inputs 608 a-f isin its home position (e.g., 180°), and these known calibrated homepositions are stored in a memory of the surgical tool 400 and accessibleby the surgical system 100 when the surgical tool 400 is coupled to thetool driver 604 (FIG. 6 ). A window or “slow zone,” which is a range ofrotational positions surrounding the known calibrated home positions atwhich the drive inputs 608 a-f may be in the home position (e.g.,180°±40°), may be built around the known calibrated home positions andsimilarly stored in a memory of the surgical tool 400 (e.g. the computersystem 606 of FIG. 6 ). The homing system may communicate with therotary encoders 630 (FIG. 6 ) to determine the angular and/or rotationalposition of each drive input 608 a-f. When the drive inputs 608 a-f arebeing rotated near the corresponding “slow zones” based on the absolutemotor position of the drivers 610 a-f as measured by the correspondingrotary encoders 630, the homing system may be programmed to decrease thespeed at which the drivers 610 a-f rotate the drive inputs 608 a-f.

FIG. 12 illustrates top, middle, and bottom graphs that illustrateoperation of an example homing system configured to intelligently adjustthe homing speed of the surgical tool 400 (FIG. 4 ) based on therotational position of the drivers 610 a-f and/or the drive inputs 608a-f operatively coupled thereto, according to one or more embodiments.In the illustrated example, the surgical tool 400 was manufactured suchthat the home position of one of the drive inputs 608 a-f occurs at anabsolute angular position of 180° and the surgical tool 400 wascalibrated to determine that the drive input 608 a-f may be rotated(clockwise or counter-clockwise) six (6) full revolutions from that homeposition until a limit is reached. The neutral position of the driveinput 608 a-f is located at the midpoint of the total range. Positionsof the sub-system before the neutral position will be negative; whereas,positions of the sub-system after the neutral position will be positive.The surgical tool 400 in this example has a gear ratio such that three(3) rotations of one of the drive inputs 608 a-f results in one (1)rotation of the end effector 404. This information may be stored in thesurgical tool 400, such as in the computer system 606 (FIG. 6 ) or thememory 624 (FIG. 6 ) of the internal computer 622 (FIG. 6 ). Mating thedrive housing 408 to the tool driver 604 places the internal computer622 in communication with the computer system 606. Also, a “slow zone”of 80° was designed to encompass that absolute angular position of thedrive input 608 a-f, thereby providing a buffer of 40° ranging beforeand after the absolute angular position of 180° (e.g., 180°±40°) whichmay correspond with the drive input 608 a-f being in a home position,and this information was also stored in the surgical tool 400.

In FIG. 12 , the top graph illustrates the angular position of the endeffector 404 in degrees versus the relative sub-system position indegrees. The surgical tool 400 in this example begins the homingprocedure in the maximum six (6) full revolutions from the homeposition. This graph shows that the sub-system starts at the negativeextreme of its position, moves towards the neutral position, andcontinues in that direction until reaching its positive extreme.

The middle graph in FIG. 12 illustrates the absolute angular measurementof the rotational position of one of the drive inputs 608 a-f in degreesversus the relative sub-system position in degrees. This graphillustrates the absolute angular position of one of the drive inputs 608a-f returning to 0° after reaching 360° because it shows the absoluteposition, rather than incremental position, of the drive inputs 608 a-f.This graph also illustrates the potential neutral position occurring atan absolute angular position of 180° that is keyed to a known relativesub-system position, and how the drivers 610 a-f may rotate the driveinputs 608 a-f six (6) full revolutions until the actual neutralposition is reached. Moreover, this graph shows the “slow zone” of 80°built around the absolute angular position of one of the drive inputs608 a-f, and how the “slow zones” are keyed to a known cumulativeposition of the driver 610 a-f.

The bottom graph in FIG. 12 illustrates how the homing system may adjustthe speed at which the drivers 610 a-f drive the drive inputs 608 a-fbased on the relative sub-system position in degrees. Here, the bottomgraph illustrates the drivers 610 a-f rotating the drive inputs 608 a-fat a first speed when the drive inputs 608 a-f are not rotationallyoriented within the “slow zones” and then stepping down the speed to asecond speed that is less than the first speed when the drive inputs 608a-f are rotationally oriented within the “slow zones.”

FIG. 13 illustrates an articulating joint 1300 for helping facilitatearticulation of the wrist 406, according to one or more embodiments ofthe present disclosure. As described above, the wrist 406 may bearticulated within a plane by antagonistically actuating a linkageassembly. More specifically, the wrist 406 may be rotated clockwise bypushing the first drive member 720 a while simultaneously pulling thesecond drive member 720 b, and the wrist 406 may be rotatedcounter-clockwise by pulling the first drive member 720 a whilesimultaneously pushing the second drive member 720 b. Accordingly, thejoint 1300 may be rotated via antagonistic translation of the first andsecond drive members 720 a,b and, as previously described, the drivemembers 720 a,b are actuated by operation of the second and third driveinputs 608 b,c (FIG. 4 ), respectively, which in turn are driven by thesecond and third drivers 610 b,c (FIG. 4 ), respectively.

During a surgical procedure, however, the end effector 404 and the wrist406 may be disposed within a body cavity and potentially abuttingpatient tissue. In such cases, the articulating joint 1300 maypotentially need to move adjacent tissue. Thus, to move the wrist 406into a desired orientation, the robotic surgical system 100 may beconfigured such that the second and third drivers 610 b,c (FIG. 4 )cause the drive members 720 a,b to translate with force sufficient toovercome any external load applied by tissue during a procedure, and tohold or maintain that desired orientation even when subjected to such anexternal load.

FIG. 14 is a schematic diagram of an example control scheme 1400 thatmay be used to control articulation of the wrist 406 via the joint 1300of FIG. 13 , according to one or more embodiments. In the illustratedexample, the control scheme 1400 utilizes an algorithm that allows forsmooth and continuous articulation of the articulation joint 1300, locksthe articulation joint 1300 so that it is cannot be moved by an externalload, and actively works against any external load as the articulationjoint 1300 is being articulated into a desired angle.

In the illustrated example, the control scheme 1400 begins at a startingpoint 1402. The control scheme 1400 first determines whether themechanism articulating the joint 1300 is properly homed, as at node1404. If the joint 1300 is not properly homed, the control scheme 1400initiates a homing sequence or homing process, as at 1406. During thehoming process of 1406, the joint 1300 is homed by eliminating any slackin the joint 1300 mechanism by antagonistically articulating (i.e.,pulling and pushing, respectively) the drive members 720 a,b equally toa prescribed torque or current for the corresponding driver 610 b,c;articulating the joint 1300 (clockwise or counter-clockwise) andrecording the angle limits to find the home positions for both drivers610 b,c; and articulating the joint 1300 to where the drivers 610 b,care in their home positions with the drive members 720 a,b being undertension and compression, respectively.

If the joint 1300 is properly homed, the clinician 112 a can direct orcommand the robot to articulate the joint 1300 to a desired articulationangle. More specifically, if the control scheme 1400 determines that themechanism of the joint 1300 is properly homed, an articulation commandinput may be provided to the control scheme 1400, as at 1408. Thearticulation command input may be indicative of the articulation angleof the joint 1300 desired by the clinician 112 a. The control scheme1400 proceeds by comparing a new articulation command of the joint 1300(i.e., “newArticulationAngleCommand”) to an old articulation command ofthe joint 1300 (i.e., “oldArticulationCommand”, as at 1410. Here, thecontrol scheme 1400 may determine whether the new articulation commandof the joint 1300 is less than, greater than, or equal to the oldarticulation command of the joint 1300. Depending on the relative valuesof the new and old articulation commands, the control scheme 1400initiates a separate articulation process, depicted herein asarticulation processes 1412 a, 1412 b, and 1412 c.

Also, the relative values of the new and old articulation commands areindicative of whether the clinician 112 a wants to move the wrist 406 ornot. For example, the clinician 112 a may want to articulate the joint1300 in a clockwise motion or in a counter-clockwise motion or maintainthe joint 1300 in a particular position. If the clinician 112 a commandsthe joint 1300 to articulate the wrist 406 in a clockwise motion, thecontrol scheme 1400 initiates the first articulation process, as at 1412a. If the clinician 112 a commands the joint 1300 to articulate thewrist 406 in a counter-clockwise motion, the control scheme 1400initiates the second articulation process, as at 1412 b. If theclinician 112 a does not command the joint 1300 to articulate the wrist406, meaning the wrist 406 is to maintain its position, the controlscheme 1400 initiates the third articulation process, as at 1412 c.

In the illustrated example, the control scheme 1400 initiates the firstarticulation process 1412 a if it determines at the decision node 1410that the new articulation command is less than the old articulationcommand, meaning that the joint 1300 is to move clockwise. Here, thefirst articulation process 1412 a puts the second driver 610 bassociated with the first drive member 720 a in its position mode andactuates the third driver 610 c into a commanded angle at a prescribedspeed limit, and the first articulation process 1412 a simultaneouslyputs the third driver 610 c associated with the second drive member 720b in torque (or current) mode to apply a prescribed torque (or current)to the third driver 610 c so that it pulls the second drive member 720 bwith a constant force.

In the illustrated example, the control scheme 1400 initiates the secondarticulation process 1412 b if it determines at the decision node 1410that the new articulation command is greater than the old articulationcommand, meaning that the joint 1300 is to move counter-clockwise. Here,the second articulation process 1412 b puts the second driver 610 bassociated with the first drive member 720 a in torque (or current) modeto apply a prescribed torque (or current) to the second driver 610 b sothat it pulls the first drive member 720 a with a constant force, andthe second articulation process 1412 b simultaneously puts the thirddriver 610 c in its position mode and actuates the third driver 610 cinto a commanded angle at a prescribed speed limit.

In the illustrated example, the control scheme 1400 initiates the thirdarticulation process 1412 c if it determines at the decision node 1410that the new articulation command equal to the old articulation command,meaning that there is no change in articulation command is the joint1300 is to remain stationary. Here, the third articulation process 1412c waits for whichever of the second or third drivers 610 b,c that is inposition mode to move into its commanded angle and then puts both thesecond and third drivers 610 b,c into position mode to hold or maintainthe joint 1300 at that position which corresponds with the desiredarticulation angle of the wrist 406.

In addition, the third articulation process 1412 c may adjust the finalcommanded angles or position of one of the second or third driver 610b,c that follows movement of the other of the second or third driver 610b,c, so that the final pre-tensioning in the drive members 720 a,b wouldbe equal to the original pre-tensioning in the drive members 720 a,b, asthe amount of torque applied by each of the drive members 720 a,b to thejoint 1300 varies depending on the angle of the joint 1300. Inparticular, say the wrist 406 of the articulation sub-system isinitially homed by moving the second and third drivers 610 b,c, so thatthere is a certain amount of pre-tensioning in the drive members 720a,b, and then the second driver 610 b is moved in response to a newarticulation command input by the clinician 112 a. As the second driver610 b is moved, thereby pulling the drive member 720 a correspondingtherewith, the other motor (i.e., the third driver 610 c) may either bedisabled (i.e., goes limp) or be put in current mode with minimalcurrent applied to it. Here, as the second driver 610 b is moved toachieve its final destination where the joint 1300 is moved into anangular position corresponding with the articulation command, the thirddriver 610 c is put into position mode and is set to a target position,and the target position is changed as a function of the articulationcommand so that the tensioning of the drive members 720 a,b would equalthe amount of pre-tensioning initially applied to the drive members 720a,b. Thus, the angular distance between the second and third drivers 610b,c may change as a function of the articulation angle of the joint1300. For example, if the second and third drivers 610 b,c are fiftydegrees (50°) apart initially to have a pre-tensioning torque of 0.1 Nm,and then the joint 1300 is articulated to an angle of ten degrees (10°),the second and third drivers 610 b,c would be moved so that they'resixty degrees (60°) apart to have equal pre-tensioning in the drivemembers 720 a,b.

FIGS. 15A and 15B illustrate example operation of the control scheme1400 of FIG. 14 . In particular, FIG. 15A illustrates application of thefirst articulation process 1412 a in controlling the drivers 610 b,c toarticulate the joint 1300 in a clockwise direction, and FIG. 15Billustrates application of the second articulation process 1412 b incontrolling the drivers 610 b,c to articulate the joint 1300 in acounter-clockwise direction. In FIG. 15A, the control scheme 1400 hasplaced the second driver 610 b in position mode, where the controlscheme 1400 polices (monitors) motion of the second driver 610 b thattranslates the first drive member 720 a, and where the control scheme1400 allows the third driver 610 c that controls the second drive member720 b to pull at a limited motor torque. In addition, the control scheme1400 has placed the third driver 610 c in torque (or current) mode wherethe third driver 610 c applies constant pulling (or pushing) to force tothe second drive member 720 b.

In FIG. 15B, the control scheme 1400 has placed the third driver 610 cin position mode, where the control scheme 1400 polices (monitors)motion of the third driver 610 c that causes translation (movement) ofthe second drive member 720 b, and where the control scheme 1400 allowsthe second driver 610 b that controls the first drive member 720 a topull at a limited motor speed. In addition, the control scheme 1400 hasplaced the second driver 610 b in torque (or current) mode where thesecond driver 610 b applies constant pulling (or pushing) to force tothe first drive member 720 a.

It is often desirable to articulate the joint 1300 as quickly aspossible to thereby enhance responsiveness of the surgical tool 400(FIG. 4 ). However, there are physical limits to the amount that thejoint 1300 may articulate and, when articulating the joint 1300 at highspeeds, the internal components of the surgical tool 400 may be damagedif the joint 1300 is articulated to its limits at elevated speeds. Forexample, impact resulting from the joint 1300 hitting its limits at highspeed may break the drive pins 1060 a,b (FIG. 10B) of the articulationmember 808 (FIGS. 9A-9B and 10A-10B) and/or the drive members 720 a,b.Thus, systems and methods are disclosed herein for controlling the joint1300 and preventing it from hitting its physical limits at elevatedspeeds, and thereby minimizing or avoiding impact on the underlyingmechanisms that articulate the joint 1300 and the wrist 406.

FIG. 16 is a schematic diagram of an alternate example control method orscheme 1600 for quickly controlling articulation of the wrist 406 whilesimultaneously preventing the joint 1300 of FIG. 13 to hit its physicallimits at high speed, according to one or more embodiments. In theillustrated example, the control scheme 1600 allows the drivers 610 b,cthat cause translation (motion) of the drive members 720 a,b, andthereby articulation of the joint 1300, to move at maximum speed when aninstantaneous angle of the joint 1300, which is estimated or measuredbased on feedback as to the position of the drivers 610 b,c, is withindefined safe limits. When the instantaneous angle of the joint 1300 isdetermined to be outside of the defined safe limits, the control scheme1600 slows the speed of the drivers 610 b,c as the joint 1300articulates at angles approaching the physical limits of the joint 1300.

The joint 1300 has a known range of articulation that defines the amountby which the wrist 406 may angle from its unarticulated position when itextends straight along the longitudinal axis A₁ of the shaft 402. Forexample, the joint 1300 may be configured to articulate clockwise orcounter-clockwise sixty degrees (60°) relative to the longitudinal axisA₁ (FIG. 4 ) before hitting its physical limits. Thus, in this example,the range of articulation of the joint 1300 would be plus or minus sixtydegrees (±60°) from the longitudinal axis A₁, such that the joint 1300has a physical limit at sixty degrees (60°) in either direction from thelongitudinal axis A₁, and thereby providing the joint 1300 with a totalof one hundred and twenty degrees (120°) of articulation. A safe limitmay be defined at any point within the range of articulation. Forexample, a safe limit may be defined at plus or minus fifty-five degrees(±55°) from the longitudinal axis A₁, such that the joint 1300 has asafety limit at fifty-five degrees (55°) in either direction from thelongitudinal axis A₁, and thereby providing the joint 1300 with a rangeof one hundred and ten degrees (110°) of articulation between the safetylimits.

In this example, the control scheme 1600 operates the drivers 610 b,c ata first speed when the joint 1300 is articulated at an instantaneousangle ∠A less than plus or minus fifty-five degrees (∠A<±55°) from thelongitudinal axis A₁, and then decreases the speed of the drivers 610b,c when the instantaneous angle ∠A of the joint 1300 is greater than orequal to fifty-five degrees (∠A 55°). Thus, the control scheme 1600slows the drivers 610 b,c when the instantaneous angle ∠A of the joint1300 approaches or is near the physical limits (e.g., ±60°∠A≤±55° andspeeds up the drivers 610 b,c when the instantaneous angle ∠A of thejoint 1300 is within the safety limits (e.g., ∠A is between −55° and55°).

When the control scheme 1600 determines that the instantaneous angle ∠Aof the joint 1300 is beyond the safety limits (e.g., −60°∠A≥−55° or55°≤∠A≤60°), the control scheme 1600 slows the drivers 610 b,c. In oneexample, the control scheme 1600 slows the drivers 610 b,c to a secondspeed that is less than the first speed at which the drivers 610 b,coperate when the instantaneous angle ∠A of the joint 1300 is within thesafety limits. In other examples, however, the control scheme 1600continuously decreases the speed of the drivers 610 b,c as the joint1300 approaches the physical limits, such that the control method 1600operates the drivers 610 b,c at a range decreasing speeds when theinstantaneous angle ∠A of the joint 1300 is beyond the safety limits.For example, the control scheme 1600 may slow the drivers 610 b,c whenthe instantaneous angle LA of the joint 1300 at the safety limit, andthen further slow the drivers 610 b,c as the instantaneous angle ∠A ofthe joint 1300 further approaches the physical limit.

Thus, after initializing the control scheme 1600, as represented by astarting point 1602 in FIG. 16 , the control scheme 1600 is configuredto receive a commanded articulation angle indicative of the angle intowhich the joint 1300 is to be articulated, as at 1604. Morespecifically, the control scheme 1600 includes an input from theclinician 112 a that represents the angle into which the clinician 112 adesires to move the wrist 406. Upon receiving the commanded articulationangle input via the input 1604, the control scheme 1600 initiates aprocess to adjust the commanded articulation angle based on a speedcontrol algorithm, as at 1606.

Upon initialization of the process, the control scheme 1600 receivesfeedback 1608 indicative of the position of the drivers 610 b,c, as at1608. Then, the control scheme 1600 uses the feedback information toestimate the current angle at which the joint 1300 is articulated, as at1610. Then, the control scheme 1600 makes a determination as to whetherthe articulation angle of the joint 1300 is close to a physical limit ofthe joint 1300, as at 1612. If the articulation angle of the joint 1300is not close to, or within a range preceding a limit, the control scheme1600 initiates an instruction to not change the commanded articulationangle (i.e., to maintain commanded articulation angle) of the joint1300, as at 1614. The control scheme 1600 may end at this point, asrepresented by a stopping point 1616. Various other systems or controlschemes may be initiated after the stopping point 1616. For example, thestopping point 1616 of the control scheme 1600 may correspond with thestarting point 1402 of the control scheme 1400 detailed above. Thus,robotic surgical system 100 may be configured to run the control scheme1600 and the control scheme 1400 in succession.

If the articulation angle of the joint 1300 is close to (or within arange preceding a limit), the control scheme 1600 initiates aninstruction causing the joint 1300 to move at a prescribed or allowablespeed before reaching the stopping point 1616, as at 1618. Thus, theinstruction will cause the drivers 610 b,c to rapidly move the joint1300 into the desired articulation angle or to the physical limit of thejoint 1300 to the extent that the desired articulation angle is withinthe permissible range of motion of the joint 1300. In the illustratedexample, the instruction at 1618 continuously compares the currentcommanded articulation angle to the previous commanded articulationangle to determine when motor positions of the drivers 610 b,c arenearing the physical limits of the joint 1300. The instruction maycalculate the allowable speed(s) at which the drivers 610 b,c operate toarticulate the joint 1300 based on how close the joint 1300 is to itsphysical limits, or based on where the joint 1300 is within a safe zoneimmediately preceding a physical limit of the joint 1300.

The control scheme 1600 may be configured to vary the speed of themotors 130 a,b as the joint 1300 articulates between its physical limitsbased on the proximity of the joint 1300 to its physical limits. Forexample, the instruction at 1618 may scale the speed of the drivers 610b,c (e.g., linearly or non-linearly) from a maximum speed to a minimumspeed as the joint 1300 approaches a physical limit. In one example, theinstruction commands the drivers 610 b,c to operate at a command speedequal to the difference between the current commanded articulation angleand the previous commanded articulation angle, divided by the time stepbetween those two measurements (i.e., CommandSpeed(CurrentCommandedArticulationAngle−PreviousCommandedArticulationAngle)/TimeStep).If the command speed is less than the allowable speed calculated by thecontrol scheme 1600, then the instruction 1618 need not change thecommanded articulation angle. But, if the command speed is greater thanor equal to the allowable speed calculated by the control scheme 1600,then the instruction 1618 changes the commanded articulation angle sothat the command speed would equal the allowable speed.

The robotic surgical system 100 of FIG. 1 may be configured to cause thesurgical tool 400 (FIG. 4 ) to accurately respond as directed by theclinician 112 a (FIG. 1 ). However, various conditions may exist (orcome into existence during use) that impair or inhibit the surgical tool400 from accurately responding to input from the clinician 112 a. Forexample, accuracy of the surgical tool 400 may be affected by conditionssuch as mechanical wear, frictional changes, user abuse, service damage,etc., and these conditions may change during use. To ensure operation ofthe surgical tool 400 correlates to commands input by the clinician 112a (i.e., positional accuracy), the robotic surgical system 100 mayinclude a robust error detection system to compensate for variousconditions that may change during use of the surgical tool 400. Sucherror detection systems may be useful for ensuring accuracy of variousfunctions of the surgical tool 400, including homing sequences,articulation of the wrist 406, closure and/or grasping of the jaws 410,412, etc. Thus, control systems and schemes are disclosed herein forensuring accuracy of the surgical tool 400 by detecting errors inposition of the surgical tool 400 based on positional values recorded onthe surgical tool 400 during manufacture.

In some embodiments, the surgical tool 400 may include physical features(or stops) that limit the various motions of the end effector 404 (FIG.4 ) and/or the wrist 406 (FIG. 4 ) to a predefined range of motion.These features may be set or calibrated into the surgical tool 400during its manufacture to correspond to various movements or positionsof the end effector 404 and/or the wrist 406. For example, the featuresmay be set during manufacture to correlate to a fully advanced positionof the end effector 404, a fully articulated position of the wrist 406,a home position of the wrist 406, or any other desired position.

As mentioned above, the surgical tool 400 may include an internalcomputer 622 (FIG. 4 ) that may include a memory 624 (FIG. 4 ), and theposition at which the physical features are set may be stored in thememory 624 and utilized as a target to determine whether it is operatingaccurately. For example, the surgical tool 400 may be calibrated duringmanufacture to determine how many rotations of a given drive input 608a-f (FIG. 6 ) is needed to move the end effector 404 and/or the wrist406 into a desired position and to determine the specific angle at whichthe drive inputs 608 a-f are oriented when in the desired position, andthis information may be stored in the memory 624. In addition, eachsurgical tool 400 may be calibrated during its manufacture to measurethe torque assumed on the drive inputs 608 a-f as they are fully rotatedfrom the home position in each direction, and this torque informationmay be recorded in the memory 624. Also, where two or more of the driveinputs 608 a-f are utilized to move the end effector 404 and/or thewrist 406, the relative position of the drive inputs 608 a-f may berecorded in the memory 624. With any or all of this information storedin the memory, the accuracy control system may provide feed specific tothe particular surgical tool 400 that is engaged in the roboticmanipulator.

In various examples, the accuracy control system may be utilized forhoming one or more of the drive inputs 608 a-f (FIG. 6 ). In exampleswhere two or more of the drive inputs 608 a-f are actuated to cause aparticular movement of the surgical tool 400 (FIG. 4 ), the actualangular position of the drive inputs 608 a-f when in the home positionand the relative position of (i.e., the angular difference between) thedrive inputs 608 a-f when in the home position are stored in the onboardmemory 624 (FIG. 6 ) of the surgical tool 400 during manufacture. Then,when the surgical tool 400 is installed on the robotic manipulator, theaccuracy control system reads the position of one of the drive inputs608 a-f as it rotates in the “home” direction, simultaneouslycalculating the position of the associated drive input(s) 608 a-f viathe relative position data stored in the memory 624, until all of theassociated drive inputs 608 a-f reach, within some error, the positionrecorded in the memory.

In examples where just one of the drive inputs 608 a-f is used to causea particular movement of the surgical tool 400, the home position of theparticular one of the drive inputs 608 a-f is stored in the memory 624(FIG. 6 ) and the accuracy control system may determine whether theparticular drive input 608 a-f is in the “home position” as thecorresponding driver 610 a-f (FIG. 6 ) rotates it in the “home”direction by comparing the actual angular position the drive input 608a-f to the “home” position stored in the memory when the surgical tool400 is mounted in the robotic manipulator. In these examples, if theparticular driver 610 a-f rotates the corresponding drive input 608 a-fless than 360°, the accuracy control system may establish the homeposition of the drive input 608 a-f when the surgical tool 400 isinstalled on the robotic manipulator. In some examples, if the travel ofany of the drive inputs 608 a-f is greater than 360°, the “home”position recorded in the memory 624 could be utilized as a confirmationcheck in combination with other homing control schemes as describedherein. Thus, the accuracy control system may check whether the driveinputs 608 a-f are in their home position(s) based on information storedin the onboard memory 624.

In some examples, the accuracy control system may be expanded tocross-check other non-home positions of the drive inputs 608 a-f. Forexample, the accuracy control system may be utilized for accuratelyrotating one or more of the drive inputs 608 a-f (FIG. 6 ) to effectuatea desired movement or position of the surgical tool 400 (FIG. 4 ) bycomparing the actual or instantaneous position of the surgical tool 400achieved during operation to a set value stored in the memory 624 (FIG.6 ). In these examples, the surgical tool 400 is calibrated duringmanufacture, with the position of the end effector 404 (FIG. 4 ) and/orthe wrist 406 (FIG. 4 ) being correlated with the position of thevarious drive inputs 608 a-f and the torque applied thereto via thecorresponding drivers 610 a-f (FIG. 6 ), and such calibrationinformation is stored in the memory 624 of the surgical tool 400. Forexample, rotational positions and/or torques of any of the drive inputs608 a-f corresponding with a fully advanced position of the end effector404 (e.g., fully expanded jaws 410, 412), fully angled position of thewrist 406, and/or a home position of the end effector 404 and/or thewrist 406, etc. may be recorded in the memory 624. This storedinformation provides a target that is specific or unique to theparticular surgical tool 400 installed in the robotic manipulator. Ifthe robotic surgical system 100 (FIG. 1 ) drives one or more of thedrivers 610 a-f to a particular position and the actually achievedposition of the end effector 404 and/or the wrist 406 of the surgicaltool 400 does not correlate with the position information stored in thememory 624, the accuracy control system will report an error inposition.

In some examples, the accuracy control system is incorporated with twoor more of the drive inputs 608 a-f (FIG. 6 ). For example, the accuracycontrol system may be utilized with the drive inputs 608 b,c thatcontrol the wrist 406 (FIG. 4 ) and/or with the drive inputs 608 d,ethat control the jaws 410, 412 (FIG. 4 ). In these examples, duringmanufacture of the surgical tool 400 the absolute angular positions oftwo or more of the drive inputs 608 a-f when the surgical tool 400 is ata set desired position (i.e., the desired position of the end effector404 and/or the wrist 406) are read and stored in the memory 624 (FIG. 6), and also the relative angular position between the drive inputs 608a-f corresponding with the set position of the surgical tool 400 (i.e.,the angular difference between the drive inputs 608 a-f) is recorded inthe memory 624. The absolute angle of the drive inputs 608 a-fcorresponds to a globally consistent angle that is consistent over timeand over robot-power cycles. For example, a graphical arrow may beprovided on the drive input 608 a-f such that it may be determined that,when such graphical arrow is aligned with a corresponding graphicalarrow on the tool driver 604 of the robot, the angle of the drive input608 a-f is “absolute zero.” When the surgical tool 400 is installed in arobotic manipulator and the clinician 112 a inputs a command to move thesurgical tool 400 to a desired position, if the actual position of thedrive inputs 608 a-f corresponding with the clinician's 112 a desiredmovement does not match the positional information stored in the memory624, the accuracy control system would report an error.

In other examples, the accuracy control system is incorporated with justone of the drive inputs 608 a-f. In these examples, the absoluteposition of one of the drive inputs 608 a-f corresponding with a setdesired position of the surgical tool 400 would be stored in its memory624 during manufacture or calibration and, during use, the accuracycontrol system could check whether the surgical tool 400 is in thedesired position.

In some examples, the accuracy control system may be configured todetect a closure error of the jaws 410, 412 (FIG. 4 ) where the actualpositions of the drive inputs 608 a-f (FIG. 6 ) corresponding with thejaws 410, 412 being closed do not match the fully-closed positions ofthe drive inputs 608 a-f set during manufacture. In some examples, theaccuracy control system may be configured to detect an opening error ofthe jaws 410, 412 where the actual positions of the drive inputs 608 a-fcorresponding with the jaws 410, 412 being fully open do not match thefully open positions of the drive inputs 608 a-f set during manufacture.In some examples, the accuracy control system may be configured todetect a grasping error of the jaws 410, 412 where the actual positionsof the drive inputs 608 a-f corresponding with the jaws 410, 412grasping at a set position relative to each other do not match thegrasping positions of the drive inputs 608 a-f set during manufacture.In some examples, the accuracy control system may be configured tomonitor the change in any of the above positions over use of thesurgical tool 400 and, if they change by a specified amount (or more),the accuracy control system may be configured report a wear error.

The robotic surgical system 100 (FIG. 1 ) may further include orincorporate a control scheme that moves the drive members 720 a,bsynchronously, meaning that, the second driver 610 b (FIG. 6 ) of thetool driver 604 (FIG. 6 ) causes translation of the first drive member720 a and the third driver 610 c causes an equal and oppositetranslation of the second drive member 720 b. For example, a left-handarticulation of the wrist 406 (FIG. 4 ) is accomplished by moving thefirst drive member 720 a proximally a distance “x” while moving thesecond drive member 720 b distally a distance “−x”. The robotic surgicalsystem 100 commands the drivers 610 b,c (that engage the drive inputs608 b,c) to rotate into motor positions necessary to cause translationof the drive members 720 a,b distances of “x” and “−x”, respectively.Thus, driver position commands R3 and R4 may be calculated tosynchronously translate the drive members 720 a,b based on an input fromthe clinician 112 a (i.e., articulationAngleCommanded). The driverposition commands R3, R4 may be calculated using the followingequations:

${x:R3} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right.}{{gear}{Radius}}}$${{- x}:R4} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right.}{{gear}{Radius}}}$

This control scheme translates input from the clinician 112 a (i.e.,articulationAngleCommanded) into rotation of the drivers 610 b,c. Inthis control scheme, the values “x” and “−x” are not directlycalculated, as the input from the clinician 112 a is the desired angleto move the wrist 406 and, from that input, the control scheme outputsthe rotary input or control of the driver 610 b,c (i.e., the driverposition commands R3, R4). To calculate “x”, the formula would bex=R3*GearRatio*2*π*gearRadius, and “−x” may be similarly calculated. Theforgoing formulae include mathematical representations of the psychicalcomponents of the surgical tool 400, where pinRadius is the distancefrom the center of the pivot shaft 1034 to the center of the drive pins1060 a,1060 b, GearRatio is the ratio created from the spur gear 709 a,bthrough the idler assembly 715 a,b (i.e., the compound gear) to thecompound pinion gear 710 a,b, and gearRadius is the radius of the secondpinion gear 713 a,b (of the compound pinion gear 710 a,b) that interactswith the drive rack 712 a,b.

This synchronous control scheme, however, may not accurately articulatethe wrist 406 into the desired articulation angle commanded by theclinician 112 a. For example, friction resulting from wear may cause thewrist 406 to articulate only 40° degrees despite the clinician 112 ahaving input a desired articulation angle of 45°. In addition todecreasing accuracy of articulation, this synchronous control scheme mayincur decreased mechanical advantage as the wrist 406 articulates atincreasing angles over time.

Thus, the robotic surgical system 100 may include improved controlschemes configured to enhance articulation of the wrist 406. In someexamples, the robotic surgical system 100 includes a differentialcontrol scheme for controlling movement of the drive members 720 a,b tomore accurately articulate the wrist 406 into the desired wrist positioninput by the clinician 112 a. In various examples, the differentialcontrol scheme may also increase the maximum angles to which the wrist406 may articulate and increase the mechanical advantage of the wrist406 (i.e., the force at which it may articulate).

The differential control scheme is a passive control that calculates thedriver position commands R3, R4 by which the drive members 720 a,b aremoved utilizing the formulae described above and modified by a constantα or a mathematical function. For example, the differential controlscheme accomplishes a left-hand articulation of the wrist 406 by movingthe first drive member 720 a a distance “x” via the first motor commandR3 while moving the second drive member 720 b a distance “−x-α” via thesecond motor command R4. Thus, one side of the articulation system maymove more (or less) than the other side. In this example described, ifthe geometry were perfect and there were no friction the constant αwould increase the tension in the system. If the constant α is aconstant then the increase in tension would be applied only when thearticulationAngleCammanded is greater (or lesser) than 0. However, theconstant α may be described as increasing or decreasing as a function ofthe articulationAngleCommanded, and, as described below, the constant αmay be an empirically determined value and/or based on a mathematicalfunction.

In some examples, the constant α may be empirically determined. In theseexamples, the constant α may be empirically determined during testing,manufacture, and/or calibration of the surgical tool 400 and, therefore,the constant α may be unique to each surgical tool 400. Here, theconstant α may act as a correction factor for the gear/linkage mechanismcontrolling the wrist 406, between a nominal condition and an actualcondition for which friction and wear (e.g., stretch of the drivemembers 720 a,b) is accounted. In one example, each of the surgicaltools 400 during manufacture is placed in a testing apparatus thatsenses articulation angle of the wrist 406 while rotating the driveinputs 608 b,c. The value of the constant α may be adjusted to minimizeerror between the actual measured articulation angle of the wrist 406and the expected articulation angle of the wrist 406, and then the valueof the constant α may be saved on the memory of the surgical tool 400 tobe utilized by the robotic surgical system 100 during an operation. Whenthe actual measured articulation angle of the wrist 406 is minimized,the value of the constant α would be flashed to the surgical tool 400 sothat the robotic surgical system 100 may use it.

In other examples, the constant α may be a value that is modified by afunction. In these examples, the constant α may be assigned a value or avalue may be empirically determined as described above. Regardless, theconstant α may be modified by various functions of the desired angleinput by the clinician 112 a (i.e., articulationAngleCommanded), such aslinear functions, sinusoidal functions, exponential functions,polynomial functions, or any combination thereof. Thus, driver positioncommands R3, R4 are calculated to translate the drive members 720 a,b adistance (i.e., “x” or “−x”) based on input from the clinician 112 a(i.e., articulationAngleCommanded) minus a correction factor, where thecorrection factor deducted from the distance is a function of thearticulationAngleCommanded multiplied by the constant α.

In one example, the correction factor is a sinusoidal function modifyingthe constant α. Here, the constant α is a value multiplied by the sin ofthe desired angle input by the clinician 112 a (i.e.,articulationAngleCommanded), such that the driver position commands R3,R4 are calculated with the following equations.

If articulationAngleCommanded is >0:

${x:R3} = {{{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}} - {\alpha*\sin\left( {{articulation}{Angle}{Commadned}*\frac{\pi}{180}} \right)}}$${{- x}:R4} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}$

If articulationAngleCommanded is <0:

${x:R3} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}$${{- x}:R4} = {{{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}} - {\alpha*\sin\left( {{articulation}{Angle}{Commadned}*\frac{\pi}{180}} \right)}}$

In another example, the correction factor is a linear function of theconstant α. Here, the constant α is a value multiplied by a linearfactor m (i.e., the slope) multiplied by the desired angle input by theclinician 112 a (i.e., articulationAngleCommanded) plus b (i.e., theintercept), such that the driver position commands R3, R4 are calculatedwith the following equations.

If articulationAngleCommanded is >0:

${x:R3} = {{{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}} - {\alpha*{m\left( {{articulation}{Angle}{Commadned}*\frac{\pi}{180}} \right)}} + b}$${{- x}:R4} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}$

If articulationAngleCommanded is <0:

${x:R3} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right.}{{gear}{Radius}}}$${R4} = {{{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}{- \alpha}*\left( {{m\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)} + b} \right)}$

In other examples, the correction factor is a polynomial function of theconstant α. For example, a polynomial function (where a, b, and c areconstants) could be as follows.

If articulationAngleCommanded is >0:

$\left. {{R3} + {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right.}{{gear}{Radius}}}} \right) - {\alpha*\left( {{a*\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)^{2}} + {b*\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)} + c} \right)}$${{- x}:R4} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}$

If articulationAngleCommanded is <0:

${x:R3} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}$${R4} = {{{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}} - {\alpha*\left( {{a*\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)^{2}} + {b*\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)} + c} \right)}}$

In other examples, the correction factor is an exponential function ofthe constant α. For example, an exponential function (where e is aconstant) could be as follows.

If articulationAngleCommanded is >0:

${R4} = {{{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}} - {\alpha*e^{({{articulation}{Angle}{Commanded}*\frac{\pi}{180}})}}}$${{- x}:R4} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}$

If articulationAngleCommanded is <0:

${x:R3} = {{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}}$${R4} = {{{Gear}{Ratio}*\left( \frac{180}{\pi} \right)*{pin}{Radius}*\frac{\sin\left( {{articulation}{Angle}{Commanded}*\frac{\pi}{180}} \right)}{{gear}{Radius}}} - {\alpha*e^{({{articulation}{Angle}{Commanded}*\frac{\pi}{180}})}}}$

FIGS. 17A and 17B are graphical representations illustrating the actualangular position output versus the desired angular input for each of thedrive inputs 608 b,c (FIG. 6 ) utilizing the foregoing equations,according to one or more embodiments. In particular, FIG. 17A plots theactual angular position obtained for the second drive input 608 b foreach desired angular position input by the clinician 112 a (i.e.,articulationAngleCommanded) under the current control scheme, thesinusoidal control scheme, and the linear control scheme. Similarly,FIG. 17B plots the actual angular position obtained for the third driveinput 608 c for each desired angular position input by the clinician 112a (i.e., articulationAngleCommanded) under the current control scheme,the sinusoidal control scheme, and the linear control scheme. Thus, asthe end effector 404 moves to the right (from center) the angulardisplacement of the right drive input increases at a greater rate thanthe left drive input, and when the end effector 404 moves to the left(from center) the angular displacement of the left drive input increasesat a greater rate than the right drive input.

The surgical tool 400 (FIG. 4 ) described and illustrated herein isconfigured as a “rotary surgical tool” because it includes rotary driveinputs 608 a-f (FIG. 6 ) that are each rotated by a corresponding driver610 a-f (FIG. 6 ) on the robotic manipulator. In other examples,however, the surgical tool 400 may be differently configured such thatit may be actuated by drivers configured to impart different types ofmechanical energy. For example, the surgical tool 400 may be configuredas a linear drive tool having one or more linear drive inputs asdescribed in U.S. Patent Application Publication No. 2018/0168745, thecontents of which are hereby incorporated by reference. In someexamples, the surgical tool 400 may include a combination of both rotaryand linear drive inputs.

In some embodiments, the robotic surgical system 100 (FIG. 1 ) mayinclude a closure control system configured to optimize the closurestroke of the closure tube 722 (FIGS. 7A-7B and 8A-8B). The closurecontrol system may monitor the stroke distance and the force applied tothe closure tube 722 during closure of the jaws 410, 412 to determinethe inflection point at which the closure tube 722 has translated toofar (i.e., over travel) along longitudinal axis A₁ (FIGS. 4, 6, and7A-7B). Thus, the closure control system may limit actuation of thedrive inputs (e.g., the fourth and fifth drive inputs 608 d,e of FIG. 6) to translate the closure tube 722 the minimum stroke distance requiredto close the jaws 410, 412 in a particular application. The closurecontrol system may thereby increase reliability of the surgical tool 400by limiting application of high forces as needed. For example, increasedforce will typically be applied to the closure tube 722 whenmanipulating thicker tissue; whereas, lesser amounts of force will beapplied when manipulating tissue having less thickness. In addition, theclosure tube 722 will not be subjected to an over-closure event duringclosure of the jaws 410, 412. Moreover, the closure control systemreduces the maximum closure stroke of the closure tube 722 as themechanism is less sensitive to mechanical variation and/or tolerance.Thus, instead of the mechanism translating the closure tube 722 to themaximum possible needed (depending on tissue variation and/or mechanicalvariation), the mechanism need only translate the closure tube 722 asufficient amount to achieve an inflection point.

FIG. 18 illustrates a force-distance graph of an exemplary closurecontrol system, according to one or more embodiments. In this example,the closure control system is configured to extend the closure tube 722(FIGS. 7A-7B and 8A-8B) by actuating the corresponding drivers (e.g.,the fourth and fifth driver 610 d,e of FIG. 6 ) corresponding with theappropriate drive inputs (e.g., the fourth and fifth drivers inputs 608d,e of FIG. 6 ). The current required to drive the drivers is recordedand equated to a force utilizing constants stored in the memory 624(FIG. 6 ) of the surgical tool 400. Also, the angular position of thedrivers is recorded and equated to a travel amount via mechanismdependent constants stored in the memory 624. As the closure tube 722 isbeing closed, the closure control system calculates the derivative offorce versus distance and utilizes a low-pass filter to remove spikes inthe curve that are caused by noise. Then, when the filtered force versusdistance derivative exceeds a mechanism-dependent threshold stored inthe memory of the surgical tool 400, the closure control system willstop further travel of the closure tube 722 and/or other closuremechanisms, and report that the surgical tool 400 is fully clamped. Uponreceiving a report that the surgical tool 400 is fully clamped, therobotic surgical system 100 (FIG. 1 ) may direct the surgical tool 400to fire and thereby transect and apply staples to the tissue clampedtherein.

Embodiments disclosed herein include:

A. A surgical tool includes a drive housing, a shaft that extends fromthe drive housing, a wrist arranged at an end of the shaft, and alinkage assembly actuatable to articulate the wrist in a plane andincluding a first drive member extending within the shaft from the drivehousing and being operatively connected to the wrist, and a second drivemember extending within the shaft from the drive housing and beingoperatively connected to the wrist. Wherein actuation of the first andsecond drive members in opposite axial directions within the shaftcauses the wrist to articulate in the plane.

B. A method of homing a rotatable drive input of a robotic surgical toolincludes recording a home position of the drive input in a memory of therobotic surgical tool, establishing a slow zone encompassing a knownangular magnitude away from the home position, and rotating the driveinput toward the home position, and slowing a rotation speed of thedrive input upon reaching the slow zone.

C. A system for controlling articulation of a joint in a surgical tooldriven by a robotic manipulator, the surgical tool having first andsecond drive members operatively coupled to the joint and arranged totranslate in opposite directions when actuated by respective first andsecond drivers of the robotic manipulator, wherein, upon receiving acommand to rotate the joint in a first rotational direction, the firstdriver actuates and thereby pushes the first drive member distally and,simultaneously, the second driver actuates and thereby pulls the seconddrive member proximally, thereby rotating the joint in the firstrotational direction, wherein, upon receiving a command to rotate thejoint in a second rotational direction opposite the first rotationaldirection, the second driver actuates and thereby pushes the seconddrive member distally and, simultaneously, the first driver actuates andthereby pulls the first drive member proximally, thereby rotating thejoint in the second rotational direction.

D. A system for controlling antagonistic translation of a pair of drivemembers in a surgical tool, the surgical tool being mountable to arobotic manipulator having a first driver operable to translate thefirst drive member and a second driver operable to translate the seconddrive member, wherein, upon receiving a desired articulation angleinput, the system determines a first driver position command and asecond driver position command at which the first and second driverswill cause translation of the first and second drive members,respectively, to achieve the desired articulation angle input, whereinthe first driver command causes the first drive member to translate adistance in a proximal direction and the second driver command causesthe second drive member to translate the distance in a distal direction,and wherein the distance is modified by a correction factor.

Each of embodiments A, B, C, and D may have one or more of the followingadditional elements in any combination: Element 1: wherein the wristincludes a base and an articulation member that is rotatable relative tothe base when acted upon by the first and second drive members. Element2: wherein the base includes a pivot shaft that is disposed within anaperture of the articulation member, the pivot shaft defining anarticulation axis about which the articulation member rotates. Element3: wherein the first drive member is coupled to a first drive pin of thearticulation member and the second drive member is coupled to a seconddrive pin of the articulation member. Element 4: wherein the linkageassembly further includes a distal link that couples distal ends of thefirst and second drive members at the wrist. Element 5: wherein thefirst drive pin of the articulation member is disposed within a firstaperture of the distal link and the second drive pin of the articulationmember is disposed within a second aperture of the distal link. Element6: wherein the base is connected to an inner grounding shaft thatextends proximally within the shaft. Element 7: wherein the first andsecond drive members are arranged within a first and second slot,respectively, defined within the inner grounding member. Element 8:wherein at least a portion of the first and second slots are definedbetween an upper surface of the inner grounding member and a lowersurface of the base. Element 9: further comprising a first drive shaftrotatably mounted within the drive housing and operatively coupled tothe first drive member such that rotation of the first drive shaftcauses axial movement of the first drive member, and a second driveshaft rotatably mounted within the drive housing and operatively coupledto the second drive member such that rotation of the second drive shaftcauses axial movement of the second drive member. Element 10: whereinthe first drive shaft is operatively coupled to the first drive membervia a first gear arrangement having a gear ratio greater than or lessthan 1:1, and the second drive shaft is operatively coupled to thesecond drive member via a second gear arrangement having a gear ratiogreater than or less than 1:1. Element 11: further comprising a firstarticulation yolk arranged around the inner grounding shaft andoperatively coupled to a proximal end of the first drive member and asecond articulation yolk arranged around the inner grounding shaft andoperatively coupled to a proximal end of the second drive member,wherein axial translation of the first and second articulation yolkscauses axial translation of the first and second drive members,respectively. Element 12: wherein the first and second articulationyolks are arranged around the inner grounding shaft such that theyrotate with the inner grounding shaft. Element 13: wherein the firstdrive shaft is operatively coupled to the first drive member via a firstdrive rack having a first yolk engageable with a first articulation yolkoperatively coupled to a proximal end of the first drive member, andwherein the second drive shaft is operatively coupled to the seconddrive member via a second drive rack having a second yolk engageablewith a second articulation yolk operatively coupled to a proximal end ofthe second drive member.

Element 14: further comprising measuring a rotational position of thedrive input with a rotary encoder. Element 15: further comprisingdetecting a torque spike with one or more torque sensors when the driveinput reaches the home position.

Element 16: wherein the first and second drivers of the roboticmanipulator maintain equal tension or compression in the first andsecond drive members until commanded to rotate the joint in either thefirst or second rotational direction. Element 17: wherein the tension orcompression applied by the first and second motors is dependent upon anarticulation angle of the joint.

Element 18: wherein the correction factor is an empirically determinedconstant of the surgical tool. Element 19: wherein the correction factoris a product of a constant and a function, and wherein the function isselected from the group consisting of a linear function, a sinusoidalfunction, an exponential function, a polynomial function, and anycombination thereof.

By way of non-limiting example, exemplary combinations applicable to A,B, C, and D include: Element 1 with Element 2; Element 1 with Element 3;Element 3 with Element 4; Element 4 with Element 5; Element 1 withElement 6; Element 6 with Element 7; Element 7 with Element 8; Element 9with Element 10; Element 7 with Element 11; Element 11 with Element 12;Element 10 with Element 13; and Element 16 with Element 17.

Therefore, the disclosed systems and methods are well adapted to attainthe ends and advantages mentioned as well as those that are inherenttherein. The particular embodiments disclosed above are illustrativeonly, as the teachings of the present disclosure may be modified andpracticed in different but equivalent manners apparent to those skilledin the art having the benefit of the teachings herein. Furthermore, nolimitations are intended to the details of construction or design hereinshown, other than as described in the claims below. It is thereforeevident that the particular illustrative embodiments disclosed above maybe altered, combined, or modified and all such variations are consideredwithin the scope of the present disclosure. The systems and methodsillustratively disclosed herein may suitably be practiced in the absenceof any element that is not specifically disclosed herein and/or anyoptional element disclosed herein. While compositions and methods aredescribed in terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps. Allnumbers and ranges disclosed above may vary by some amount. Whenever anumerical range with a lower limit and an upper limit is disclosed, anynumber and any included range falling within the range is specificallydisclosed. In particular, every range of values (of the form, “fromabout a to about b,” or, equivalently, “from approximately a to b,” or,equivalently, “from approximately a-b”) disclosed herein is to beunderstood to set forth every number and range encompassed within thebroader range of values. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee. Moreover, the indefinite articles “a” or “an,” as used in theclaims, are defined herein to mean one or more than one of the elementsthat it introduces. If there is any conflict in the usages of a word orterm in this specification and one or more patent or other documentsthat may be incorporated herein by reference, the definitions that areconsistent with this specification should be adopted.

As used herein, the phrase “at least one of” preceding a series ofitems, with the terms “and” or “or” to separate any of the items,modifies the list as a whole, rather than each member of the list (i.e.,each item). The phrase “at least one of” allows a meaning that includesat least one of any one of the items, and/or at least one of anycombination of the items, and/or at least one of each of the items. Byway of example, the phrases “at least one of A, B, and C” or “at leastone of A, B, or C” each refer to only A, only B, or only C; anycombination of A, B, and C; and/or at least one of each of A, B, and C.

What is claimed is:
 1. A method of homing a drive input of a roboticsurgical tool, comprising: recording and storing a home position of thedrive input in a memory included in the robotic surgical tool;establishing a slow zone for the drive input encompassing a knownangular magnitude away from the home position; storing the slow zone inthe memory; rotating the drive input toward the home position; andslowing a rotation speed of the drive input upon reaching the slow zone.2. The method of claim 1, wherein rotating the drive input toward thehome position includes: mounting the robotic surgical tool to a tooldriver of a robotic manipulator, the tool driver including a drivermatable with the drive input, and a motor that drives the driver inrotation to thereby rotate the drive input; sending an input signal tothe motor to operate the driver and thereby rotate the drive input; andmeasuring rotational motion of the motor with a rotary encodercommunicably coupled to the motor and thereby determining an angularposition of the drive input.
 3. The method of claim 1, furthercomprising detecting a torque spike with one or more torque sensors whenthe drive input reaches the home position.
 4. The method of claim 1,wherein recording and storing the home position of the drive input inthe memory comprises: calibrating the robotic surgical tool duringmanufacture of the robotic surgical tool and thereby determining anabsolute angular position at which the drive input reaches the homeposition; and storing the absolute angular position in the memory as thehome position.
 5. The method of claim 1, wherein the drive inputrequires rotation of two or more full revolutions prior to reaching thehome position, the method further comprising establishing the slow zonefor each full revolution of the drive input; and slowing the rotationspeed of the drive input upon reaching each slow zone.
 6. The method ofclaim 1, wherein slowing the rotation speed of the drive input uponreaching the slow zone comprises: rotating the drive input at a firstspeed when the drive input is not rotationally oriented within the slowzone; and rotating the drive input at second speed slower than the firstspeed when the drive input is rotationally oriented within each slowzone.
 7. A homing system for a robotic surgical tool including a drivehousing and a drive input rotatably mounted to the drive housing, thehoming system comprising: a memory included in an internal computerforming part of the drive housing, the memory having stored therein: ahome position of the drive input; and a slow zone established for thedrive input that encompasses a known angular magnitude away from thehome position; and a computer system in communication with the memoryand in further communication with a motor operable to rotate the driveinput and a rotary encoder operable to determine an angular position ofthe drive input, wherein the computer system causes the motor to reducea rotation speed of the drive input upon reaching the slow zone.
 8. Thehoming system of claim 7, further comprising one or more torque sensorsoperatively coupled to the motor and in communication with the computersystem, wherein the one or more torque sensors detect a torque spikewhen the drive input reaches the home position.
 9. The homing system ofclaim 7, wherein the home position of the drive input is 180° and theslow zone comprises a buffer of 40° ranging before and after theabsolute angular position of 180°.
 10. The homing system of claim 7,wherein the drive input requires rotation of two or more fullrevolutions prior to reaching the home position, and wherein the slowzone comprises a corresponding slow zone for each full revolution of thedrive input.
 11. The homing system of claim 10, wherein computer systemis programmed to slow the rotation speed of the drive input uponreaching each slow zone.
 12. The homing system of claim 7, wherein thedrive input is rotated at a first speed when the drive input is notrotationally oriented within the slow zone, and wherein the drive inputis rotated at second speed slower than the first speed when the driveinput is rotationally oriented within each slow zone.
 13. A roboticsurgical tool, comprising a drive housing having first and second driveinputs rotatably coupled thereto, the drive housing being mountable to atool driver of a robotic manipulator, and the tool driver includingfirst and second drivers matable with the first and second drive inputs;a shaft extending from the drive housing and terminating at an endeffector; a wrist joint interposing the shaft and the end effector; afirst drive member extending from the drive housing and terminating atthe wrist joint, the first drive member being operatively coupled to thefirst drive input such that actuation of the first driver moves thefirst drive member along the shaft; and a second drive member extendingfrom the drive housing and terminating at the wrist joint, the seconddrive member being operatively coupled to the second drive input suchthat actuation of the second driver moves the second drive member alongthe shaft, wherein the wrist joint is rotated a first rotationaldirection by actuating the first driver and thereby pushing the firstdrive member distally while simultaneously actuating the second driverand thereby pulling the second drive member proximally, and wherein thewrist joint is rotated a second rotational direction by actuating thefirst driver and thereby pulling the first drive member proximally whilesimultaneously actuating the second driver and thereby pushing thesecond drive member distally.
 14. The robotic surgical tool of claim 13,wherein the first and second drivers maintain equal tension orcompression in the first and second drive members until commanded torotate the wrist joint in either the first or second rotationaldirections.
 15. The robotic surgical tool of claim 14, wherein thetension or compression applied by the first and second drivers isdependent upon an articulation angle of the joint.
 16. The roboticsurgical tool of claim 13, wherein the wrist joint includes physicallimits past which the wrist joint cannot physically rotate, the homingsystem further comprising: a computer system in communication with firstand second motors arranged to drive the first and second drivers,respectively, wherein the computer system is programmed to operate thefirst and second motors at a first speed when an instantaneous angle ofthe wrist joint is within a defined safe limit away from the physicallimits, and wherein the computer system is programmed to operate thefirst and second motors at a second speed lower than the first speedwhen the instantaneous angle of the wrist joint is outside the definedsafe limit and near the physical limits.
 17. The robotic surgical toolof claim 16, wherein the first and second motors decelerate at aconstant speed when transitioning between the first and second speeds.18. A system for controlling antagonistic translation of a pair of drivemembers in a surgical tool, the surgical tool being mountable to arobotic manipulator having a first driver operable to translate thefirst drive member and a second driver operable to translate the seconddrive member, wherein, upon receiving a desired articulation angleinput, the system determines a first driver position command and asecond driver position command at which the first and second driverswill cause translation of the first and second drive members,respectively, to achieve the desired articulation angle input, whereinthe first driver command causes the first drive member to translate adistance in a proximal direction and the second driver command causesthe second drive member to translate the distance in a distal direction,and wherein the distance is modified by a correction factor.
 19. Thesystem of claim 18, wherein the correction factor is an empiricallydetermined constant of the surgical tool.
 20. The system of claim 18,wherein the correction factor is a product of a constant and a function,and wherein the function is selected from the group consisting of alinear function, a sinusoidal function, an exponential function, apolynomial function, and any combination thereof.